Insulated glazing units

ABSTRACT

A hermetically sealed multi-pane window assembly comprises first and second windowpane sheets formed of transparent materials. A first sealing member has an inner edge and an outer edge, the inner edge being hermetically attached around the periphery of the first windowpane sheet by diffusion bonding. A second sealing member has an inner edge and an outer edge, the inner edge being hermetically attached around the periphery of the second windowpane sheet by diffusion bonding and the outer edge being hermetically attached to the outer edge of the first sealing member. A spacer assembly is disposed between the first and the second windowpane sheets for maintaining a gap therebetween, whereby a hermetically sealed cavity is defined between the first and the second windowpanes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.11/381,733, filed May 4, 2006, published on Aug. 24, 2006, as U.S.Publication No. 2006-0187608, now U.S. Pat. No. 7,832,177, issued onNov. 16, 2010. Application Ser. No. 11/381,733 is a Continuation-In-Partof U.S. patent application Ser. No. 10/766,493, filed Jan. 27, 2004,published on Sep. 30, 2004, as U.S. Publication No. 2004-0188124, nowabandoned. Application Ser. No. 11/381,733 also claims benefit of U.S.Provisional Application Nos. 60/707,367, filed Aug. 11, 2005 and60/678,570, filed May 6, 2005. Application Ser. No. 10/766,493 is aContinuation-In-Part of U.S. patent application Ser. No. 10/713,475,filed Nov. 14, 2003, published on Jun. 3, 2004, as U.S. Publication No.2004-0104460, now U.S. Pat. No. 6,962,834, issued on Nov. 8, 2005.Application Ser. No. 10/766,493 also claims benefit of U.S. ProvisionalApplication Nos. 60/531,882, filed Dec. 22, 2003; 60/454,922, filed Mar.13, 2003; 60/442,922, filed Jan. 27, 2003; and 60/442,941, filed Jan.27, 2003. Application Ser. No. 10/713,475 is a Continuation-In-Part ofU.S. patent application Ser. No. 10/133,049, filed Apr. 26, 2002,published on Oct. 9, 2003, as U.S. Publication No. 2003-0188881, nowU.S. Pat. No. 6,723,379, issued on Apr. 20, 2004. Application Ser. No.10/713,475 also claims benefit of U.S. Provisional Application Nos.60/442,922, filed Jan. 27, 2003; 60/442,941, filed Jan. 27, 2003; and60/426,522, filed Nov. 15, 2002. Application Ser. No. 10/133,049 is aContinuation-In-Part of U.S. patent application Ser. No. 10/104,315,filed Mar. 22, 2002, now U.S. Pat. No. 6,627,814, issued on Sep. 30,2003.

U.S. Pat. Nos. 7,832,177; 6,962,834; 6,723,379; 6,627,814; and PatentApplication Publication Nos. 2006-0187608; 2004-0188124; 2004-0104460;2003-0188881 are hereby incorporated by reference.

TECHNICAL FIELD OF THE INVENTION

The current invention relates to thermally insulated building windows,and more particularly to multi-pane glazing units having a vacuum or athermally insulating material disposed in the space between thewindowpanes.

BACKGROUND OF THE INVENTION

Photonic, photovoltaic, optical and micro-mechanical devices aretypically packaged such that the active elements (i.e., the emitters,receivers, micro-mirrors, etc.) are disposed within a sealed chamber toprotect them from handling and other environmental hazards. In manycases, it is preferred that the chamber be hermetically sealed toprevent the influx, egress or exchange of gasses between the chamber andthe environment. Of course, a window must be provided to allow light orother electromagnetic energy of the desired wavelength to enter and/orleave the package. In some cases, the window will be visiblytransparent, e.g., if visible light is involved, but in other cases thewindow may be visibly opaque while still being “optically” transparentto electromagnetic energy of the desired wavelengths. In many cases, thewindow is given certain optical properties to enhance the performance ofthe device. For example, a glass window may be ground and polished toachieve certain curve or flatness specifications in order to disperse ina particular pattern and/or avoid distorting the light passingtherethrough. In other cases, anti-reflective or anti-refractivecoatings may be applied to the window to improve light transmissiontherethrough.

Hermetically sealed micro-device packages with windows have heretoforetypically been produced using cover assemblies with metal frames andglass window panes. To achieve the required hermetic seal, the glasswindow pane (or other transparent window material) has heretofore beenfused to its metallic frame by one of several methods. A first of thesemethods is heating it in a furnace at a temperature exceeding thewindow's glass transition temperature, T_(G) and/or the window'ssoftening temperature T_(S) (typically at or above 900° C.). However,because the fusing temperature is above T_(G) or T_(S), the originalsurface finish of the glass pane is typically ruined, making itnecessary to finish or re-finish (e.g., grinding and polishing) bothsurfaces of the window pane after fusing in order to obtain thenecessary optical characteristics. This polishing of the window panesrequires additional process steps during manufacture of the coverassemblies, which steps tend to be relatively time and labor intensive,thus adding significantly to the cost of the cover assembly, and henceto the cost of the overall package. In addition, the need to polish bothsides of the glass after fusing requires the glass to project both aboveand below the attached frame. This restricts the design options for thecover assembly with respect to glass thickness, dimensions, etc., whichcan also result in increased material costs.

A second method to hermetically attach a transparent window to a frameis to solder the two items together using a separate preform made of ametal or metal-alloy solder material. The solder preform is placedbetween a pre-metallized window and a metal or metallized frame, and thesoldering is performed in a furnace. During soldering, no significantpressure is applied, i.e., the parts are held together with only enoughforce to keep them in place. For this type of soldering, the most commonsolder preform material is eutectic gold-tin.

Eutectic gold-tin solder melts and solidifies at 280 degrees Celsius.Its CTE at 20 degree is 16 ppm/° C. These two characteristics causethree drawbacks to the reliability of the assembled window. First, theCTE of Mil-Spec kovar from 280° C. to ambient is approximately5.15+/−0.2 ppm/0 C, while most window glasses intended for sealing tokovar have higher average CTEs over the same temperature range. Duringcooling from the set point of 280° down to ambient, the glass isshrinking at a greater rate than the kovar frame it's attached to. Thecooled glass will be in tension, which is why it is prone to cracking.To avoid cracking, the glass should have an identical or slightly loweraverage CTE than the kovar so as to be stress neutral or in slightcompression after cooling. Using solders with lower liquidus/solidustemperatures puts the kovar at a higher average CTE, more closelymatching the average CTE of the glass. However, this worsens the seconddrawback of metal-allow solder seals.

The second drawback to soldering the glass to the kovar frame is thatthe window assembly will delaminate at temperatures above the liquidustemperature of the employed solder. Using lower liquidus/solidustemperature solders, while reducing the CTE mismatch between the kovarand glass, further limits the applications for the window assembly. Mostlead-free solders have higher liquidus/solidus temperatures than the183° C. of eutectic Sn/Pb. Surface-Mount Technology (SMT) reflow ovensare profiled to heat Printed-Wiring Board (PWB) assemblies 15-20 degreesabove the solder's liquidus/solidus temperature. So the SMTreflow-soldering attachment to a PWB of a MOEMS device whose window wasmanufactured using lower melting-point solder preforms might have theunfortunate effect of reflowing the window assembly's solder, causingwindow delamination.

The third drawback is that the solder, which is the intermediate layerbetween the glass and the kovar frame, has a CTE up to three timesgreater than the two materials it's joining. An intermediate joiningmaterial would ideally have a compensating CTE in-between the twomaterials it's bonding.

A third method to hermetically attach a glass window to a frame is tosolder the two items together using a solder-glass material.Solder-glasses are special glasses with a particularly low softeningpoint. They are used to join glass to other glasses, ceramics, or metalswithout thermally damaging the materials to be joined. Soldering iscarried out in the viscosity range h where h is the range from 10⁴ to10⁶ dPa s (poise) for the solder-glass; this corresponds generally to atemperature range T (for the glass solder or solder-glass) within therange from 350° C. to 700° C.

Once a cover assembly with a hermetically sealed window is prepared, itis typically seam welded to the device base (i.e., substrate) in orderto produce the finished hermetically sealed package. Seam welding uses aprecisely applied AC current to produce localized temperatures of about1,100° C. at the frame/base junction, thereby welding the metallic coverassembly to the package base and forming a hermetic seal. To preventdistortion of the glass windowpane or package, the metal frame of thecover assembly should be fabricated from metal or metal alloy having aCTE (i.e., coefficient of thermal expansion) that is similar to that ofthe transparent window material and to the CTE of the package base.

While the methods described above have heretofore produced useablewindow assemblies for hermetically sealed micro-device packages, therelatively high cost of these window assemblies is a significantobstacle to their widespread application. A need therefore exists, forpackage and component designs and assembly methods, which reduce thelabor costs associated with producing each package.

A need still further exists for package and component designs andassembly methods that will minimize the manufacturing cycle timerequired to produce a completed package.

A need still further exists for package and component designs andassembly methods that reduce the number of process steps required forthe production of each package. It will be appreciated that reducing thenumber of process steps will reduce the overhead/floor space required inthe production facility, the amount of capital equipment necessary formanufacturing, and handling costs associated with transferring the workpieces between various steps in the process. A reduction in the cost oflabor may also result. Such reductions would, of course, further reducethe cost of producing these hermetic packages.

A need still further exists for package and component designs andassembly methods that will reduce the overall materials costs associatedwith each package, either by reducing the initial material cost, byreducing the amount of wastage or loss during production, or both.

Many types of multi-pane insulated window assemblies are known. Aconventional multi-pane insulated window assembly consists, at aminimum, of two windowpanes joined by a frame that maintains a spacebetween them. The space is filled with air or another thermallyinsulating material, typically a gas. Multi-pane insulated windowassemblies typically have better thermal insulation properties thansingle-pane windows; however, further improvement in insulatingperformance is often desired.

A vacuum-glazing unit (VGU) is a window assembly similar to a multi-paneinsulated window assembly, except a vacuum or partial vacuum ismaintained in the space between the windowpanes. The purpose of thistype of construction is to produce an insulated window unit with ahigher level of thermal insulation that can be obtained from air- orgas-filled insulated window assemblies. To date, however, many problemshave been experienced in producing durable and reliable VGUs. Forexample, it has proven difficult to achieve seals between thewindowpanes and the frame having the hermeticity necessary to maintain avacuum (or partial vacuum) for an extended period. Further, it hasproven difficult to produce VGUs for exterior wall installations (i.e.,for use in the outside-facing (exterior) walls and doors of buildings)that can withstand large and/or rapid thermal cycling (e.g., caused bychanges in outside temperatures and/or use of high-performance HVACsystems) without eventually leaking or cracking. A need thereforeexists, for improved VGUs and methods of producing durable and reliableVGUs suitable for use in exterior walls and doors, as well as for otherapplications.

A Jun. 10, 2005 Department of Energy (DOE) solicitation states that thekey technical challenges associated with highly insulating fenestrationproducts include, but are not limited to: larger size (˜25 sq. ft. andlarger), improved durability, excessive weight, seal durability, andhigh cost. Without an aggressive program to change the energy-relatedrole of windows in buildings, it will thus be virtually impossible tomeet Zero Energy Buildings goals. The DOE's Window Technology IndustryRoadmap (Roadmap), published by the Office of Building Technology, Stateand Community Programs (BTS), after listing several areas of windowtechnology in need of improvements, states such improvements have notbeen realized due to factors including: High-first-cost of improvedproducts; the cost and questionable durability of existinghighly-insulating window technologies; the lack of industrycollaboration to improve insulation technology and manufacturingmethods; and the presumed high-risk-low-return ratio of investments inimproved technologies.

In fact, the window industry has not improved the basic technology orreliability of insulating windows for decades. Manufacturers use anadhesive to bond pairs of windowpanes to an intermediate spacer toachieve an airtight cavity between the windowpanes. No epoxy, glue orother adhesive in use today is airtight. All permit some amount of gasexchange to occur. According to data published in 2002 by The SealedInsulated Glass Manufacturers Association (SIGMA), warranty claims forinstalled insulated glass (IG) window units due to seal failures is 4%ten years after installation, and almost 10% fifteen years afterinstallation. Most window units do not identify the manufacturer. Manyhomeowners consciously or inadvertently choose to live with the failedwindow seals and water condensation between the IG windowpanes thatreduce energy efficiency. The majority of IG unit (IGU) seal failuresare not considered in the SIGMA data. The actual number of IGU sealfailures 15 years after installation is unknown and believed to be veryhigh. All of these conditions are bleeding us of energy.

Some academic institutions, companies and government labs have triedachieving higher insulating values (higher R-value; lower U-value) whileattempting to solve the issue of leaking seals. Their solutions all havefour things in common: The units contain a vacuum between windows #1 and#2 to provide higher insulation than a fill gas; mechanical spacers areused to maintain the separation of the window lites (i.e., panes) #1 and#2 (if the lites come in physical contact with each other, this createsan undesirable thermal path that substantially reduces the IG unit'sinsulating value); the lites are hermetically sealed at their perimeters(most P commonly, using reflowed solder glass to seal two closelyseparated lites, and less commonly, using a laser to melt the two litestogether); and all currently produced or described vacuum glazing unitsemploy a tube (i.e., “pinch-tube”) to evacuate the IG unit, after whichthe tube is sealed shut.

These experimental solutions are not commercially available in the U.S.because they have failed or have not proven to be reliable. Problemsinclude: the spacers are opaque or not aesthetically appealing so theyfail to meet industry needs; laser attempts at sealing have resulted inbroken lites due to thermal shocking of the glass; high thermalconductivity between the perimeter surfaces of the inside of the glasslites where they are sealed together; stress eventually causes eitherthe seal or the lites to break because the sealing method is notcompliant (flexible); elevated soldering temperatures eliminate theability to use some soft-coat low-e coatings; and/or when a vacuum tubeis added, it increases the unit's complexity and decreases itsreliability.

A need therefor exists, for vacuum glazing units (VGUs) and insulatedglass units (IGUs) having improved designs which address some of theaforesaid problems with the current technology.

SUMMARY OF THE INVENTION

The present invention disclosed herein comprises, in one aspect thereof,a hermetically sealed multi-pane window assembly. The window assemblycomprises first and second windowpane sheets formed of transparentmaterials. A first sealing member has an inner edge and an outer edge,the inner edge being hermetically attached around the periphery of thefirst windowpane sheet by diffusion bonding. A second sealing member hasan inner edge and an outer edge, the inner edge being hermeticallyattached around the periphery of the second windowpane sheet bydiffusion bonding and the outer edge being hermetically attached to theouter edge of the first sealing member. A spacer assembly is disposedbetween the first and the second windowpane sheets for maintaining a gaptherebetween, whereby a hermetically sealed cavity is defined betweenthe first and the second windowpanes.

The present invention disclosed herein comprises, in another aspectthereof, a method for manufacturing a hermetically sealed multi-panewindow assembly. A first windowpane sheet formed of a transparentmaterial and having a periphery is provided, as is a first sealingmember having an inner edge and an outer edge. The inner edge of thefirst sealing member is positioned against the first windowpane sheet.The inner edge of the first sealing member is pressed against the firstwindowpane sheet with sufficient force to produce a first predeterminedcontact pressure between the inner edge and the windowpane sheet along afirst junction region. The first junction region is heated to produce afirst predetermined temperature along the first junction region. Thefirst predetermined contact pressure and an elevated temperature aremaintained until a diffusion bond is formed between the first sealingmember and the first windowpane sheet around the periphery of the firstwindowpane sheet. A second windowpane sheet formed of a transparentmaterial and having a periphery is provided, as is a second sealingmember having an inner edge and an outer edge. The inner edge of thesecond sealing member is positioned against the second windowpane sheet.The inner edge of the second sealing member is pressed against thesecond windowpane sheet with sufficient force to produce a secondpredetermined contact pressure between the inner edge and the windowpanesheet along a second junction region. The second junction region isheated to produce a second predetermined temperature along the secondjunction region. The second predetermined contact pressure and anelevated temperature are maintained until a diffusion bond is formedbetween the second sealing member and the second windowpane sheet aroundthe periphery of the second windowpane sheet. A spacer assembly ispositioned between the first and the second windowpane sheets formaintaining a gap therebetween. The outer end of the first sealingmember is hermetically connected to the outer end of the second sealingmember, whereby a hermetically sealed cavity is defined between thefirst and the second windowpanes.

The present invention disclosed herein comprises, in a further aspectthereof, a hermetically sealed multi-pane window assembly comprising afirst windowpane formed of a transparent material and having aperiphery. A first sealing member has an inner edge and an outer edge.The inner edge is hermetically sealed to the first windowpane around theperiphery. A second windowpane is formed of a transparent material andhas a periphery. The second windowpane is spaced-apart from the firstwindowpane. A second sealing member has an inner edge and an outer edge.The inner edge is hermetically sealed to the second windowpane aroundthe periphery, and the outer edge is hermetically attached to the outeredge of the first sealing member. At least one of the first and secondsealing members is compliant to enable relative movement between thefirst and second windowpanes. In this manner, a hermetically sealedcavity is formed between the first and the second windowpanes.

The present invention addresses many limitations of the prior art and,in various embodiments, provides VGUs and/or IGUs having some or all ofthe following advantages: diffusion bonding is used to makeglass-to-metal, glass-to-glass and/or metal-to-metal bonds that arepermanent, i.e., they cannot be disassembled by any known means suchthat the seals may last for up to 80 years; the hermetic sealing systemincorporates a compliant (i.e., flexible) sleeve/frame unit (also calleda “bellows”) that acts as springs, allowing the outside-facing windowlite (window #1) to expand and contract due to temperature changesindependent of the inside-facing lite (window #2); the metal sleeves arebonded to the glass lites using a glass-to-metal diffusion bondingprocess, and thus are more hermetic (gas-tight) than other knownglass-to-metal seals; the thin, flexible metal sleeves have a highthermal resistance so that they do not adversely impact the overallinsulating value; the windowpanes of the invention are able to use anycurrently employed glazing and coating, including low-e and UV-blockingcoatings, and are also be compatible with electrochromeric coatings;units of the current invention can be thinner to reduce the weight anddepth of the product, whether the application is a commercial windowwall or a fenestration product; and spacer systems that are nearlyinvisible from any viewing angle.

Additional embodiments of the invention address the need for a drop-inreplacement system for the single-pane glass units still used in themajority of U.S. buildings. IGUs of the invention can be thin enough toreplace the 6 mm (¼″) thick single pane windows now in the majority ofU.S. buildings, and may be economically installed so that vast numbersof owners could achieve significant heating and cooling energyreductions without incurring substantial window replacement costs.

Still further embodiments of the invention produce insulating windowsaddressing all of the DOE concerns and needs. In one such embodiment,the invention is an IGU that employs a partial vacuum instead of a fillgas to increase its insulating value.

In another embodiment, the invention comprises an IGU that contains avacuum in the cavity between the pairs of windowpanes. A vacuum is theultimate thermal insulator. The higher the level of vacuum, the fewerthe molecules available to transfer heat between the pairs ofwindowpanes. Thus, window assemblies containing a vacuum instead of agas will have the highest theoretical thermal insulation value (U-Value)of any window unit composed of two or more panes of glass or othermaterials.

In a further embodiment, the invention comprises an IGU having compliant(flexible) metal sleeves/frames (also known as “bellows”) thathermetically seal the IG unit, providing highest reliability while alsopossessing high thermal resistance (low thermal conductance) to minimizetheir impact on the unit's overall thermal performance.

In a still further embodiment, the invention comprises an IGU employingglass-to-metal diffusion bonding to bond the flexible metal sleeves tothe glass lites (windows #1 and #2). This bond is permanent because itis molecular in nature, and is more hermetic than any other knownattachment method. The IGU may contain and maintain a vacuum upwards of80 years.

In yet another embodiment, the invention comprises an IGU that employs aunique glass spacer system of a glass substrate with glass standoffs onthe top and bottom substrate surfaces. Any coatings that can be appliedto surfaces #2 or #3 of known IGUs can instead be applied to eithersurface of the glass spacer substrate. IGU surfaces #2 and #3 can becoated with a scratch-resistant thin-film material such as diamond-likecoatings (DLC) so that the differential movement of the glass spacersand the lites they support do not produce scratches on the lites' insidesurfaces.

In another embodiment, the invention comprises an IGU having thinnerwindows, which reduce the weight and depth of the fenestration products.Reducing the frame and associated construction materials will alsoreduce weight.

In a further embodiment, the invention comprises an IGU for residentialand small commercial use that may be made as thin or thinner than the 6mm (¼″) thick single-pane windows now installed in the majority ofhomes, thereby simplifying and/or reducing the cost of upgrading to asuper insulating IG unit in existing fenestration products.

In a still further embodiment, the invention comprises an IGU thateliminates breakage due to bulging at high altitude.

The present invention disclosed and claimed herein comprises, in anotheraspect thereof, a frame assembly for hermetic attachment to one side ofa sheet of transparent material having a plurality of window apertureareas defined thereon, each window aperture area being circumscribed bya frame attachment area having a predefined plan. The frame assemblycomprises a plurality of continuous sidewalls circumscribing a pluralityof frame apertures such that some sidewalls are disposed between twoadjacent frame apertures. The sidewalls have an upper side planconfigured to substantially correspond with the predefined plans of theframe attachment areas of the sheet. The sidewalls disposed between theadjacent frame apertures include two generally parallel sidewall membershaving an overall vertical thickness and a first connecting tabextending therebetween. When viewed in cross-section taken perpendicularto the plan view, the configuration of the sidewalls disposed betweenadjacent frame apertures is characterized by the first connecting tabhaving a relatively constant vertical thickness that is significantlysmaller than the overall vertical thickness of the adjacent sidewallmembers.

The present invention disclosed and claimed herein comprises, in anotheraspect thereof, a frame assembly for hermetic attachment to one side ofa sheet of transparent material having a plurality of window apertureareas defined thereon, each window aperture area being circumscribed bya frame attachment area having a predefined plan. The frame assemblycomprises a first layer having a plan including a plurality ofcontinuous sidewalls circumscribing a plurality of frame apertures suchthat some sidewalls are disposed between two adjacent frame apertures.The sidewalls have an upper side plan configured to substantiallycorrespond with the predefined plans of the frame attachment areas ofthe sheet. A second layer has a plan including a plurality of continuoussidewalls. The sidewalls of the second layer have an upper side planconfigured to at least partially overlap the plan of the sidewalls ofthe first layer all the way around each frame aperture. The first andsecond layers are joined to one another to create a hermeticallygas-tight frame around each frame aperture.

The present invention disclosed and claimed herein comprises, in yetanother aspect thereof, a hermetically sealed multi-pane windowassembly. The window assembly comprises a spacer having a continuoussidewall circumscribing and thereby defining an aperture therethrough.The sidewall has an upper sealing surface and a lower sealing surface.The upper sealing surface is disposed on the upper side of the sidewalland continuously circumscribes the aperture, and the lower sealingsurface is disposed on the lower side of the sidewall and continuouslycircumscribes the aperture. The window assembly further comprises afirst and a second transparent windowpane sheets. The first sheet isdisposed over at least a part of the upper sealing surface continuouslyaround the aperture, and the second sheet is disposed over at least apart of the lower sealing surface continuously around the aperture,thereby defining a cavity enclosed by the sidewall and the windowpanesheets. The first and second transparent windowpane sheets are eachhermetically bonded to the spacer without non-hermetic adhesives to forma continuous hermetic joint around the aperture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a hermetically sealed micro-devicepackage;

FIG. 2 is a cross-sectional view of the micro-device package of FIG. 1;

FIG. 3 is an exploded view of a cover assembly manufactured inaccordance with one embodiment of the current invention;

FIGS. 4 a and 4 b show transparent sheets having contoured sides,specifically:

FIG. 4 a showing a sheet having both sides contoured;

FIG. 4 b showing a sheet having one side contoured;

FIG. 5 shows an enlarged view of the sheet seal-ring area prior tometallization;

FIG. 6 shows an enlarged view of the sheet seal-ring area aftermetallization;

FIG. 7 shows a cross-sectional view through a pre-fabricated frame;

FIG. 8 illustrates placing the frame against the metallized sheet priorto bonding;

FIG. 9 is a block diagram of a process for manufacturing coverassemblies using prefabricated frames in accordance with one embodiment;

FIG. 10 is an exploded view of a cover assembly manufactured using asolder preform;

FIG. 11 is a partial perspective view of another embodiment utilizingsolder applied by inkjet;

FIGS. 12 a-c and FIGS. 13 a-c illustrate a process of manufacturingcover assemblies in accordance with yet another embodiment of theinvention, specifically:

FIG. 12 a shows the initial transparent sheet;

FIG. 12 b shows the transparent sheet after initial metallization;

FIG. 12 c shows the transparent sheet after deposition of the integralframe/heat spreader;

FIG. 13 a shows a partial cross-section of the sheet of FIG. 12 a;

FIG. 13 b shows a partial cross-section of the sheet of FIG. 12 b;

FIG. 13 c shows a partial cross-section of the sheet of FIG. 12 c;

FIG. 14 is a block diagram of a process for manufacturing coverassemblies using cold gas dynamic spray technology in accordance withanother embodiment;

FIGS. 15 a-15 b illustrate a multi-unit assembly manufactured inaccordance with another embodiment; specifically:

FIG. 15 a illustrates an exploded view of a the multi-unit assembly;

FIG. 15 b is bottom view of the frame of FIG. 15 a;

FIG. 16 a illustrates compliant tooling formed in accordance withanother embodiment;

FIG. 16 b is a side view of a multi-unit assembly illustrating themethod of separation;

FIGS. 17 a and 17 b illustrate the manufacture of multiple coverassemblies in accordance with yet another embodiment, specifically:

FIG. 17 a shows the transparent sheet in its original state;

FIG. 17 b illustrates the sheet after deposition of the multi-apertureframe/heat spreader;

FIGS. 18 a-18 c illustrate an assembly configuration suitable for usewith electrical resistance heating; specifically:

FIG. 18 a illustrates the configuration of the sheet;

FIG. 18 b illustrates the configuration of the frame;

FIG. 18 c illustrates the joined sheet and frame;

FIGS. 19 a-19 f illustrate multi-unit assembly configurations suitablefor heating with electrical resistance heating;

FIG. 20 a illustrates an exploded view of a window assembly includinginterlayers for diffusion bonding;

FIG. 20 b illustrates the window assembly of FIG. 20 a after diffusionbonding;

FIGS. 20 c and 20 d illustrate an additional embodiment of the inventionhaving internal and external frames; specifically:

FIG. 20 c illustrates an exploded view of a “sandwiched” window assemblybefore bonding;

FIG. 20 d illustrates the completed assembly of FIG. 20 c after bonding;

FIGS. 20 e, 20 f and 20 g, illustrate fixtures for aligning andcompressing the window assemblies during diffusion bonding;specifically:

FIG. 20 e illustrates an empty fixture and clamps;

FIG. 20 f illustrates the fixture of FIG. 20 e with a window assemblypositioned therein for bonding;

FIG. 20 g illustrates an alternative fixture designed to produce moreaxial pressure on the window assembly;

FIGS. 21 a-21 b are cross-sectional views of wafer-level hermeticmicro-device packages in accordance with other embodiments of theinvention; specifically:

FIG. 21 a shows a wafer-level hermetic micro-device packages havingreverse-side electrical connections;

FIG. 21 b shows a wafer-level hermetic micro-device package havingsame-side electrical connections;

FIG. 21 c is an exploded view illustrating the method of assembly of thepackage of FIG. 21 b;

FIG. 22 illustrates a semiconductor wafer having a multiplemicro-devices formed thereupon suitable for multiple simultaneouswafer-level packaging;

FIG. 23 illustrates the semiconductor wafer of FIG. 22 aftermetallization of the wafer surface;

FIG. 24 illustrates a metallic frame for attachment between the wafersurface and the window sheet of a hermetic package;

FIGS. 25 a-25 d show enlarged views of the frame members of FIG. 24;specifically:

FIG. 25 a is a top view of a portion of a double frame member prior tosingulation;

FIG. 25 b is an end view of the double frame member of FIG. 25 a;

FIG. 25 c is a top view of a portion of a single frame member from theperimeter of the frame, or after device singulation; and

FIG. 25 d is an end view of the single frame member of FIG. 25 c;

FIG. 26 illustrates a metallized window sheet for attachment to theframe of FIG. 24;

FIG. 27 shows a cross-sectional side view of a multiple-package assemblyprior to singulation;

FIG. 28 illustrates one option for singulation of the multiple-packageassembly of FIG. 27;

FIG. 29 illustrates another option for singulation of themultiple-package assembly of FIG. 27;

FIG. 30 illustrates a semiconductor wafer after metallization of thewafer surface in accordance with another embodiment having an electrodeplacement portion;

FIG. 31 illustrates a metallized window sheet in accordance with anotherembodiment having an electrode placement portion;

FIG. 32 is a cross-sectional side view of a multiple-package assemblyprior to singulation in accordance with another embodiment having directelectrode access;

FIG. 33 is a top view of a micro-device with same-side pads;

FIG. 34 illustrates a semiconductor wafer having formed thereon aplurality of the micro-devices of FIG. 33;

FIG. 35 illustrates the semiconductor wafer of FIG. 34 aftermetallization of the wafer surface;

FIG. 36 illustrates a metallic frame for attachment to the wafer surfaceof FIG. 35;

FIG. 37 illustrates a metallized window sheet for attachment to theframe of FIG. 36;

FIG. 38 shows a top view a complete multiple-package assembly;

FIG. 39 illustrates a multi-package strip after column separation of themultiple-package assembly of FIG. 38;

FIG. 40 illustrates a single packaged micro-device after singulation ofthe multiple-package strip of FIG. 39;

FIG. 41 illustrates a partial cross-sectional side view of amultiple-package assembly having an alternative frame design prior tosingulation;

FIGS. 42 a-42 e are cross-sectional side views of alternative framedesigns, each showing a pair of adjacent frame side members joined by aconnecting tab;

FIGS. 43 a-43 e are cross-sectional side views of additional alternativeframe designs, each showing a pair of adjacent frame side members joinedby one or more connecting tabs;

FIGS. 44 a-44 e are cross-sectional side views of further alternativeframe designs, each showing a pair of adjacent frame side members joinedby a connecting tab;

FIGS. 45 a-45 f are cross-sectional side views of still otheralternative frame designs, each showing a pair of adjacent frame sidemembers joined by one or more connecting tabs;

FIGS. 46 a-46 d are partial plan views of alternative frame designs,each showing a pair of adjacent frame side members joined by aconnecting tab;

FIG. 47 is a plan view of a frame assembly fabricated by photo-chemicalmachining (PCM);

FIG. 48 is a cross-sectional side view of the frame assembly of FIG. 47;

FIG. 49 is a perspective view of a PCM-fabricated multiple-frame arrayprior to singulation;

FIG. 50 is an exploded view of a double-pane hermetic window assembly;

FIG. 51 is a perspective view of the assembled double-pane hermeticwindow assembly of FIG. 50;

FIG. 52 is an exploded view of a building window unit including twodouble-pane hermetic window assemblies;

FIG. 53 is a perspective view of the assembled building window unit ofFIG. 52;

FIG. 54 is an exploded view of a triple-pane hermetic window assembly;

FIG. 55 is a perspective view of the assembled triple-pane hermeticwindow assembly of FIG. 54;

FIG. 56 illustrates the apparatus for fixturing multiple sets ofhermetic window assemblies for simultaneous bonding;

FIG. 57 is a double-pane vacuum glazing unit (“VGU”) in accordance withthe PRIOR ART;

FIG. 58 a is an exploded view of the components of a vacuum glazing unitin accordance with one embodiment;

FIG. 58 b is an assembled view of the VGU of FIG. 58 a;

FIGS. 58 c, 58 d and 58 e illustrate joining/bonding the upper framemember to the lower frame member;

FIG. 58 f is a perspective view of a compliant frame in accordance withanother embodiment;

FIG. 59 a is an exploded view of the components of a vacuum glazing unitincorporating a woven spacer in accordance with another embodiment;

FIG. 59 b is an assembled view of the VGU of FIG. 59 a;

FIG. 60 a exploded view of the components of a VGU with optionalinterlayers in accordance with another embodiment;

FIG. 60 b is an assembled view of the VGU of FIG. 60 a;

FIG. 61 a is an exploded view of the components of a VGU with thespacers incorporated into the fabrication of the lower windowpane inaccordance with another embodiment;

FIG. 61 b is an assembled view of the VGU of FIG. 61 a;

FIG. 62 a is a side view of a windowpane with spacers on one of itssurfaces that are incorporated into the windowpane's fabrication inaccordance with another embodiment;

FIG. 62 b is a first perspective view of the windowpane with spacers ofFIG. 62 a;

FIG. 62 c is a second perspective view of the windowpane with spacers ofFIG. 62 a;

FIG. 63 a is an exploded view of the components of a VGU with atransparent sheet center spacer unit that is fabricated with stand-offson (as part of) the sheet's top and bottom sides in accordance withanother embodiment;

FIG. 63 b is an assembled view of the VGU of FIG. 63 a;

FIG. 64 a is an exploded view of the components of a VGU with anoptional member between the sealed frame members and the windowpanes inaccordance with another embodiment;

FIG. 64 b is an assembled view of the VGU of FIG. 64 a;

FIG. 65 a is an exploded view of the components of a VGU with upper andlower frame members of similar shape and size in accordance with anotherembodiment;

FIG. 65 b is an assembled view of the VGU of FIG. 65 a;

FIGS. 66 a, 66 b and 66 c show three variations on the “gull-wing”cross-sectional profile of the frame member;

FIG. 67 a is a perspective view of an assembly of horizontal andvertical muntin bars in accordance with another embodiment;

FIG. 67 b is a perspective view of an assembly of horizontal andvertical muntin bars with standoffs in accordance with anotherembodiment;

FIG. 67 c is a side view of the muntin bar assembly of FIG. 67 b;

FIG. 67 d is an exploded view of the muntin bar assembly of FIG. 67 bpositioned between the upper windowpane and the lower windowpane to forma sub-assembly;

FIG. 67 e is an assembled perspective view of the sub-assembly of FIG.67 d;

FIG. 67 f is an assembled side view of the sub-assembly of FIG. 67 d;

FIG. 67 g is an exploded view showing components of a VGU utilizing themuntin and windowpane sub-assembly of FIG. 67 f;

FIG. 67 h is an assembled view showing the VGU of FIG. 67 g;

FIG. 68 a is an exploded view of a VGU with frame members bonded to theinner (inside) surfaces of the windowpanes in accordance with anotherembodiment;

FIG. 68 b is an assembled view showing the VGU of FIG. 68 a;

FIG. 69 a is an exploded view of a VGU with an internal muntin assemblyand with inside-the windowpane bonded frame members that extend past theouter surfaces of the upper and lower windowpanes in accordance withanother embodiment;

FIG. 69 b is an assembled view showing the VGU of FIG. 69 a;

FIG. 70 a is an exploded view of a VGU with inside-the-windowpane bondedframe members and optional interlayers between the frame members and thewindowpanes in accordance with another embodiment;

FIG. 70 b is an assembled view showing the VGU of FIG. 70 a;

FIG. 71 a shows a VGU with a center spacer unit in accordance withanother embodiment;

FIG. 71 b shows a VGU with a center spacer unit and an intermediateframe member that is attached to the center spacer unit in accordancewith yet another embodiment;

FIG. 71 c shows a VGU with a center spacer unit and an intermediateframe member that is attached to the center spacer unit in accordancewith a still further embodiment;

FIG. 72 a is an exploded view of the components of a VGU with upper andlower windowpanes having built-on spacers and a flat center spacer inaccordance with another embodiment;

FIG. 72 b is an assembled view of the VGU of FIG. 72 a;

FIG. 73 a is an exploded view of the components of a vacuum glazing unitin accordance with another embodiment;

FIG. 73 b is an assembled view of the VGU of FIG. 73 a;

FIG. 73 c is a perspective view of a compliant frame in accordance withanother embodiment;

FIG. 74 is a side view of a spacer unit for a vacuum glazing unit inaccordance with one embodiment;

FIG. 75 is a side view of a spacer unit for a vacuum glazing unit inaccordance with another embodiment;

FIG. 76 is a side view of a spacer unit for a vacuum glazing unit inaccordance with a further embodiment having “laminated” or “sandwiched”construction;

FIG. 77 is an enlarged elevation view of a portion of the spacer unitwith cross-shaped stand-offs;

FIG. 78 is another elevation view of a portion of the spacer unit withcross-shaped stand-offs;

FIG. 79 is an enlarged elevation view of a portion of the spacer unitwith “C”-shaped stand-offs.

FIG. 80 is a cross-sectional view of a two-lite IGU with spacer inaccordance with another embodiment;

FIG. 81 is a cross-sectional view of a three-lite gas-filled IGU inaccordance with another embodiment;

FIG. 82 is a cross-sectional view of a three-lite IGU with spacer inaccordance with another embodiment;

FIG. 83 is a top view, with portions broken away, of the IGU of FIG. 80;

FIG. 84 is a cross-sectional view of a two-lite IGU with spacer inaccordance with another embodiment;

FIG. 85 is an enlarged cross-sectional perspective view of the spacerand retainer bar of FIG. 84;

FIG. 86 is the spacer and retainer bar of FIG. 85 showing the connectionthereof;

FIG. 87 is a cross-sectional view of a three-lite IGU with inside framemounting and spacers in accordance with another embodiment;

FIG. 88 is an enlarged portion of the IGU of FIG. 87;

FIG. 89 is a cross-sectional view of a two-lite IGU with spacer inaccordance with another embodiment;

FIG. 90 shows the IGU of FIG. 89 supported by a mounting block inaccordance with another embodiment;

FIG. 91 a shows the IGU and mounting block of FIG. 90 mounted in aframe;

FIG. 91 b shows a unitary combined frame in accordance with anotherembodiment;

FIG. 92 is a perspective view of a portion of the mounting block of FIG.90;

FIG. 93 is a top view of a portion of the mounting block of FIG. 92;

FIG. 94 a shows a two-pane IGU having an anchored spacer in accordancewith another embodiment;

FIG. 94 b shows a two-pane IGU having no spacer in accordance withanother embodiment;

FIG. 95 shows a three-pane IGU having split anchored spacers inaccordance with still another embodiment; and

FIGS. 96 a, 96 b and 96 c are perspective views showing assembly of anIGU with flexible spacers in accordance with another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The current invention is described below in greater detail withreference to certain preferred embodiments illustrated in theaccompanying drawings.

Referring now to FIGS. 1 and 2, there is illustrated a typicalhermetically sealed micro-device package for housing one or moremicro-devices. For purposes of this application, the term “micro-device”includes photonic devices, photovoltaic devices, optical devices (i.e.,including reflective, refractive and diffractive type devices),electro-optical and electro-optics devices (EO devices), light emittingdevices (LEDs), liquid crystal displays (LCDs), liquid crystal onsilicon (LCOS) technologies which includes direct drive image lightamplifiers (D-ILA), opto-mechanical devices, micro-optoelectromechanicalsystems (i.e., MOEMS) devices and micro-electromechanical systems (i.e.,MEMS) devices. The package 102 comprises a base or substrate 104, whichis hermetically sealed to a cover assembly 106 comprising a frame 108and a transparent window 110. A micro-device 112 mounted on the base 104is encapsulated within a cavity 114 when the cover assembly 106 isjoined to the base 104. One or more electrical leads 116 may passthrough the base 104 to carry power, ground, and signals to and from themicro-device 112 inside the package 102. It will be appreciated that theelectrical leads 116 must also be hermetically sealed to maintain theintegrity of the package 102. The window 110 is formed of an opticallyor electro-magnetically transparent material. For purposes of thisapplication, the term “transparent” refers to materials, which allow thetransmission of electromagnetic radiation having predeterminedwavelengths, including, but not limited to, visible light, infraredlight, ultraviolet light, microwaves, radio waves, or x-rays. The frame108 is formed from a material, typically a metal alloy, which preferablyhas a CTE close to that of both the window 110 and the package base 104.

Referring now to FIG. 3, there is illustrated an exploded view of acover assembly manufactured in accordance with one embodiment of thecurrent invention. The cover assembly 300 includes a frame 302 and asheet 304 of a transparent material. The frame 302 has a continuoussidewall 306, which defines a frame aperture 308 passing therethrough.The frame sidewall 306 includes a frame seal-ring area 310 (denoted bycrosshatching) circumscribing the frame aperture 308. Since the frame302 will eventually be welded to the package base 104 (from FIGS. 1 and2,) it is usually formed of a weldable metal or alloy, preferably onehaving a CTE very close to that of the micro-device package base 104. Insome embodiments, however, the cover assembly frame 304 may be formed ofa non-metallic material such as ceramic or alumina. Regardless ofwhether the frame 302 is formed of a metallic or non-metallic material,the surface of the frame seal-ring area 310 is preferably metallic(e.g., metal plated if not solid metal) to facilitate the hermeticsealing of the sheet 304 to the frame. In a preferred embodiment, theframe is primarily formed of an alloy having a nominal chemicalcomposition of 54% iron (Fe), 29% nickel (Ni) and 17% cobalt (Co). Suchalloys are also known by the designation ASTM F-15 alloy and by thetrade name Kovar Alloy. As used in this application, the term “KovarAlloy” will be understood to mean the alloy having the chemicalcomposition just described. In embodiments where a Kovar Alloy frame 302is used, it is preferred that the surface of the frame seal-ring area310 have a surface layer of gold (Au) overlying a layer of nickel (Ni),or a layer of nickel without the overlaying gold. The frame 302 alsoincludes a base seal area 320, which is adapted for eventual joining,typically by welding, to the package base 104. The base seal area 320frequently includes a layer of nickel overlaid by a layer of gold tofacilitate seam welding to the package base. Although the gold overnickel surface layers are only required along the base seal-ring area320, it will be appreciated that in many cases, for example, wheresolution bath plating is used to apply the surface materials, the goldover nickel layers may be applied to the entire surface of the frame302. The sheet 304 can be any type of transparent material, for example,soft glass (e.g., soda-lime glass), hard glass (e.g. borosilicateglass), crystalline materials such as quartz and sapphire, or polymericmaterials such as polycarbonate plastic. In addition to opticallytransparent materials, the sheet 304 may be visibly opaque buttransparent to non-visible wavelengths of energy. As previouslydiscussed, it is preferred that the material of the sheet 304 have a CTEthat is similar to that of the frame 304 and of the package base 104 towhich the cover assembly will eventually be attached. For manysemiconductor photonic, photovoltaic, MEMS or MOEMS applications, aborosilicate glass is well suited for the material of the sheet 304.Examples of suitable glasses include Corning 7052, 7050, 7055, 7056,7058, 7062, Kimble (Owens Corning) EN-1, and Kimble K650 and K704. Othersuitable glasses include Abrisa soda-lime glass, Schott 8245 and OharaCorporation S-LAM60.

The sheet 304 has a window portion 312 defined thereupon, i.e., this isthe portion of the sheet 302 which must remain transparent to allow forthe proper functioning of the encapsulated, i.e., packaged, micro-device112. The window portion 312 of the sheet has top and bottom surfaces 314and 316, respectively, that are optically finished in the preferredembodiment. The sheet 304 is preferably obtained with the top and bottomsurfaces 314 and 316 of the window portion 312 in ready to use form,however, if necessary the material may be ground and polished orotherwise shaped to the desired surface contour and finish as apreliminary step of the manufacturing process. While in many cases thewindow portion 312 will have top and bottom surfaces of 314 and 316 thatare optically flat and parallel to one another, it will be appreciatedthat in other embodiments at least one of the finished surfaces of thewindow portion will be contoured. A sheet seal-ring area 318 (denotedwith cross-hatching) circumscribes the window portion 312 of the sheet304, and provides a suitable surface for joining to the front seal-ringarea 310.

Referring now to FIGS. 4 a and 4 b, there are illustrated transparentsheets having contoured sides. In FIG. 4 a, transparent sheet 304′ hasboth a curved top side 314′ and a curved bottom side 316′ producing awindow portion 312 having a curved contour with a constant thickness. InFIG. 4 b, sheet 304 has a top side 314, which is curved, and a bottomside 316, which is flat, thereby resulting in a window portion 312having a plano-convex lens arrangement. It will be appreciated that insimilar fashion (not illustrated) the finished surfaces 314 and 316 ofthe window portion 312 can have the configuration of a refractive lensincluding a plano-convex lens as previously illustrated, a double convexlens, a plano-concave lens or a double concave lens. Other surfacecontours may give the finished surfaces of the window portion 312 theconfiguration of a Fresnel lens or of a diffraction grating, i.e., “adiffractive lens.”

In many applications, it is desirable that window portion 312 of thesheet 304 have enhanced optical or physical properties. To achieve theseproperties, surface treatments or coatings may be applied to the sheet304 prior to or during the assembly process. For example, the sheet 304may be treated with siliconoxynitride (SiOn) to provide a harder surfaceon the window material. Whether or not treated with SiOn, the sheet 304may be coated with a scratch resistant/abrasion resistant material suchas amorphous diamond-like carbon (DLC) such as that sold by Diamonex,Inc., under the name Diamond Shield®. Other coatings which may beapplied in addition to, or instead of, the SiOn or diamond-like carboninclude, but are not limited to, optical coatings, anti-reflectivecoatings, refractive coatings, achromatic coatings, optical filters,solar energy filters or reflectors, electromagnetic interference (EMI)and radio frequency (RF) filters of the type known for use on lenses,windows and other optical elements. It will be appreciated that theoptical coatings and/or surface treatments can be applied either on thetop surface 314 or the bottom surface 316, or in combination on bothsurfaces, of the window portion 312. It will be further appreciated,that the optical coatings and treatments just described are notillustrated in the figures due to their transparent nature.

In some applications, a visible aperture is formed around the windowportion 312 of the sheet 304 by first depositing a layer ofnon-transparent material, e.g., chromium (Cr), sometimes coating thematerial over the entire surface of the sheet and then etching thenon-transparent material from the desired aperture area. This procedureprovides a sharply defined border to the window portion 312, which isdesirable in some applications. This operation may be performed prior toor after the application of other treatments depending on thecompatibility and processing economics.

The next step of the process of manufacturing the cover assembly 300 isto prepare the sheet seal-ring area 318 for metallization. The sheetseal-ring area 318 circumscribes the window portion 312 of the sheet304, and for single aperture covers is typically disposed about theperimeter of the bottom surface 316. It will be appreciated, however,that in some embodiments the sheet seal-ring area 318 can be located inthe interior portion of a sheet, for example where the sheet will bediced to form multiple cover assemblies (i.e., as described laterherein). The sheet seal-ring area 318 generally has a configuration,which closely matches the configuration of the frame seal-ring area 310to which it will eventually be joined. Preparing the sheet seal-ringarea 318 may involve a thorough cleaning to remove any greases, oils orother contaminants from the surface, and/or it may involve rougheningthe seal-ring area by chemical etching, laser ablating, mechanicalgrinding or sandblasting this area. This roughening increases thesurface area of the sheet seal-ring, thereby providing increasedadhesion for the subsequently deposited metallization materials, if thesheet seal-ring is to be metallized prior to joining to the frameseal-ring area 310 or to other substrates or device package bases.

Referring now to FIG. 5, there is illustrated a portion of the sheet 304which has been placed bottom side up to better illustrate thepreparation of the sheet seal-ring area 318. In this example theseal-ring area 318 has been given a roughened surface 501 to improveadhesion of the metallic layers to be applied. Chemical etching toroughen glass and similar transparent materials is well known.Alternatively, laser ablating, conventional mechanical grinding orsandblasting may be used. A grinding wheel with 325 grit is believedsuitable for most glass materials, while a diamond grinding wheel may beused for sapphire and other hardened materials. The depth 502 to whichthe roughened surface 501 of the sheet seal-ring area 318 penetrates thesheet 304 is dependent on at least two factors: first, the desiredmounting height of the bottom surface 316 of the window relative to thepackage bottom and/or the micro-device 112 mounted inside the package;and second, the required thickness of the frame 306 including all of thedeposited metal layers (described below). It is believed that etching orgrinding the sheet seal-ring area 318 to a depth of 502 within the rangefrom about 0 inches to about 0.05 inches will provide a satisfactoryadhesion for the metallized layers as well as providing an easilydetectable “lip” for locating the sheet 304 in the proper positionagainst the frame 306 during subsequent joining operations.

It will be appreciated that it may be necessary or desirable to protectthe finished surfaces 314 and/or 316 in the window portion 312 of thesheet (e.g., the portions that will be optically active in the finishedcover assembly) from damage during the roughening process. If so, thesurfaces 314 and/or 316 may be covered with semiconductor-grade “tackytape” or other known masking materials prior to roughening. The maskmaterial must, of course, be removed in areas where the etching/grindingwill take place. Sandblasting is probably the most economical method ofselectively removing strips of tape or masking material in the regionsthat will be roughened. If sandblasting is used, it could simultaneouslyperform the tape removal operation and the roughening of the underlyingsheet.

Referring now to FIG. 6, there is illustrated a view of the seal-ringarea 318 of the sheet 304 after metallization. The next step of themanufacturing process may be to apply one or more metallic layers to theprepared sheet seal-ring area 318. The current invention contemplatesseveral options for accomplishing this metallization. A first option isto apply metal layers to the sheet seal-ring area 318 using conventionalchemical vapor deposition (CVD) technology. CVD technology includesatmospheric pressure chemical vapor deposition (APCVD), low pressurechemical vapor deposition (LPCVD), plasma assisted (enhanced) chemicalvapor deposition (PACVD, PECVD), photochemical vapor deposition (PCVD),laser chemical vapor deposition (LCVD), metal-organic chemical vapordeposition (MOCVD) and chemical beam epitaxy (CBE). A second option formetallizing the roughened seal-ring area 318 is using physical vapordeposition (PVD) technology. PVD technology includes sputtering, ionplasma assist, thermal evaporation, vacuum evaporation, and molecularbeam epitaxy (MBE). A third option for metallizing the roughened sheetseal-ring area 318 is using solution bath plating technology (SBP).Solution bath plating includes electroplating, electroless plating andelectrolytic plating technology. While solution bath plating cannot beused for depositing the initial metal layer onto a nonmetallic surfacesuch as glass or plastic, it can be used for depositing subsequentlayers of metal or metal alloy to the initial layer. Further, it isenvisioned that in many cases, solution bath plating will be the mostcost effective metal deposition technique. Since the use of chemicalvapor deposition, physical vapor deposition and solution bath plating todeposit metals and metal alloys is well known, these techniques will notbe further described herein.

A fourth option for metallizing the sheet seal-ring area 318 of thesheet 304 is so-called cold-gas dynamic spray technology, also known as“cold-spray”. This technology involves the spraying of powdered metals,alloys, or mixtures of metal and alloys onto an article using a jet ofhigh velocity gas to form continuous metallic coating at temperatureswell below the fusing temperatures of the powdered material. Details ofthe cold-gas dynamic spray deposition technology are disclosed in U.S.Pat. No. 5,302,414 to Alkhimov et al. It has been determined thataluminum provides good results when applied to glass using the cold-gasdynamic spray deposition. The aluminum layer adheres extremely well tothe glass and may create a chemical bond in the form of aluminumsilicate. However, other materials may also be applied as a first layerusing cold-spray, including tin, zinc, silver and gold. Since thecold-gas dynamic spray technology can be used at low temperatures (e.g.,near room temperature), it is suitable for metallizing materials havinga relatively low melting point, such as polycarbonates or otherplastics, as well as for metallizing conventional materials such asglass, alumina, and ceramics.

For the initial metallic layer deposited on the sheet 304, it isbelieved that any of chromium, nickel, aluminum, tin, tin-bismuth alloy,gold, gold-tin alloy can be used, this list being given in what isbelieved to be the order of increasing adhesion to glass. Othermaterials might also be appropriate. Any of these materials can beapplied to the sheet seal-ring area 318 using any of the CVD or PVDtechnologies (e.g., sputtering) previously described. After the initiallayer 602 is deposited onto the sheet seal-ring area 318 of thenonmetallic sheet 304, additional metal layers, e.g., second layer 604,third layer 606 and fourth layer 608 (as applicable) can be added by anyof the deposition methods previously described, including solution bathplating. It is believed that the application of the following rules willresult in satisfactory thicknesses for the various metal layers. RuleNo. 1: the minimum thickness, except for the aluminum or tin-basedmetals or alloys, which will be bonded to the gold-plated Kovar alloyframe: 0.002 microns. Rule 2: the minimum thickness for aluminum ortin-based metals or alloys deposited onto the sheet or as the finallayer, which will be bonded to the gold-plated Kovar alloy frame: 0.8microns. Rule 3: the maximum thickness for aluminum or tin-based metalsor alloys deposited onto the sheet or as the final layer, which will bebonded to the gold-plated Kovar alloy frame: 63.5 microns. Rule 4: themaximum thickness for metals, other than chromium, deposited onto thesheet as the first layer and which will have other metals or alloysdeposited on top of them: 25 microns. Rule 5: the maximum thickness formetals, other than chromium, deposited onto other metals or alloys asintermediate layers: 6.35 microns. Rule 6: the minimum thickness formetals or alloys deposited onto the sheet or as the final layer, whichwill act as the solder for attachment to the gold-plated Kovar alloyframe: 7.62 microns. Rule 7: the maximum thickness for metals or alloysdeposited onto the sheet or as the final layer, which will act as thesolder for attachment to the gold-plated Kovar alloy frame: 101.6microns. Rule 8: the maximum thickness for chromium: 0.25 microns. Rule9: the minimum thickness for gold-tin solder, applied via inkjet orsupplied as a solder preform: 6 microns. Rule 10: the maximum thicknessfor gold-tin solder, applied via inkjet or supplied as a solder preform:101.6 microns. Rule 11: The minimum thickness for immersion zinc; 0.889microns. Note that the above rules apply to metals deposited using alldeposition methods other than cold-gas dynamic spray deposition.

For cold spray applications, the following rules apply: Rule 1: theminimum practical thickness for any metal layer: 2.54 microns. Rule 2:the maximum practical thickness for the first layer, and all additionallayers, but not including the final Kovar alloy layer: 127 microns. Rule3: the maximum practical thickness for the final Kovar alloy layer:12,700 microns, i.e., 0.5 inches.

By way of example, not to be considered limiting, the following metalcombinations are believed suitable for seal-ring area 318 when bondingthe prepared sheet 304 to a Kovar alloy-nickel-gold frame 302 (i.e.,Kovar alloy core plated first with nickel and then with gold) usingthermal compression (TC) bonding, or sonic, ultrasonic or thermosonicbonding.

The assembly sequence can also be to first bond the frame/spacer andwindow sheet together to form a hermetically sealed window unit, andlater, to bond this window unit to the substrate. A third assemblysequence can also be to first bond the frame/spacer and substratetogether and later, to bond this substrate/frame/spacer unit to thewindow. In some instances, an intermediate material, also referred to asan interlayer material, may be employed between the substrate and theframe/spacer and/or between the frame/spacer and the window sheet. Itwill be understood that, while the examples described herein arebelieved suitable for metallizing the seal-ring surface of a sheet orlens prior to bonding in applications where metallization is used, insome other embodiments employing diffusion bonding (i.e., thermalcompression bonding), metallization of the seal-ring area on the sheetor lens may be omitted altogether when joining the sheet/lens to theframe or another substrate of the device package base.

Example 1

Min. Max. Layers Metal Deposition (microns) (microns) 1 A1 CVD, PVD 0.763.5

Example 2

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD0.002 25 2 Cu CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Sn or SnBi CVD, PVD, SBP 0.7 63.5

Example 3

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD0.002 25 2 Zn CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Sn or Sn—Bi CVD, PVD, SBP 0.7 63.5

Example 4

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD0.002 25 2 Zn CVD, PVD, SBP 0.002 6.35 3 Sn or Sn—Bi CVD, PVD, SBP 0.763.5

Example 5

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn (de-stressed)CVD, PVD 0.002 25 2 Cu CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.0026.35 4 Sn or Sn—Bi CVD, PVD, SBP 0.7 63.5

Example 6

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn—Bi CVD, PVD0.7 63.5

Example 7

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15 2 Ni CVD, PVD, SBP 0.002 6.35 3 Sn or Sn—Bi CVD, PVD, SBP 0.763.5

Example 8

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15 2 Ni CVD, PVD, SBP 0.002 6.35 3 Al CVD, PVD, SBP 0.7 63.5

Example 9

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15 2 Ni CVD, PVD, SBP 0.002 6.35 3 Zn CVD, PVD, SBP 0.002 6.35 4Al CVD, PVD, SBP 0.7 63.5

Example 10

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD0.002 152.4 2 Sn or Sn—Bi CVD, PVD, SBP 0.7 63.5

Example 11

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD0.002 152.4 2 Al CVD, PVD, SBP 0.7 63.5

Example 12

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD0.002 152.4 2 Zn CVD, PVD, SBP 0.002 6.35 3 A1 CVD, PVD, SBP 0.7 63.5

Example 13

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn CVD, PVD 0.763.5

Example 14

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15

Example 15

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD0.002 152.4

Example 16

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn—Bi CVD, PVD0.7 63.5

By way of further example, not to be considered limiting, the followingmetal combinations and thicknesses are preferred for seal-ring area 318when bonding the prepared sheet 304 to a Kovar alloy-nickel-gold frame302 using thermal compression (TC) bonding, or sonic, ultrasonic orthermosonic bonding.

Example 17

Min. Max. Layers Metal Deposition (microns) (microns) 1 A1 CVD, PVD 150.8

Example 18

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD 0.12.54 2 Cu CVD, PVD, SBP 0.25 2.54 3 Ni CVD, PVD, SBP 1 5.08 4 Sn or SnBiCVD, PVD, SBP 1 50.8

Example 19

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD 0.12.54 2 Zn CVD, PVD, SBP 0.3175 5.08 3 Ni CVD, PVD, SBP 1 5.08 4 Sn orSn—Bi CVD, PVD, SBP 1 50.8

Example 20

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD 0.12.54 2 Zn CVD, PVD, SBP 0.3175 5.08 3 Sn or Sn—Bi CVD, PVD, SBP 1 50.8

Example 21

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn (de-stressed)CVD, PVD 0.1 2.54 2 Cu CVD, PVD, SBP 0.25 2.54 3 Ni CVD, PVD, SBP 1 5.084 Sn or Sn—Bi CVD, PVD, SBP 1 50.8

Example 22

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn—Bi CVD, PVD 150.8

Example 23

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Ni CVD, PVD, SBP 1 5.08 3 Sn or Sn—Bi CVD, PVD, SBP 1 50.8

Example 24

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Ni CVD, PVD, SBP 1 5.08 3 Al CVD, PVD, SBP 1 50.8

Example 25

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Ni CVD, PVD, SBP 1 5.08 3 Zn CVD, PVD, SBP 0.3175 5.08 4 Al CVD,PVD, SBP 1 50.8

Example 26

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD 0.15.08 2 Sn or Sn—Bi CVD, PVD, SBP 1 50.8

Example 27

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD 0.15.08 2 A1 CVD, PVD, SBP 1 50.8

Example 28

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD 0.15.08 2 Zn CVD, PVD, SBP 0.3175 5.08 3 A1 CVD, PVD, SBP 1 50.8

Example 29

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn CVD, PVD 150.8

Example 30

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12

Example 31

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD 0.150.8

Example 32

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn—Bi CVD, PVD 150.8

As indicated above, the previous examples are believed suitable forapplication of, among other processes, thermal compression bonding. TCbonding is a process of diffusion bonding in which two prepared surfacesare brought into intimate contact, and plastic deformation is induced bythe combined effect of pressure and temperature, which in turn resultsin atom movement causing the development of a crystal lattice bridgingthe gap between facing surfaces and resulting in bonding. TC bonding cantake place at significantly lower temperatures than many other forms ofbonding such as braze soldering.

Referring now to FIG. 7, there is illustrated a cross-sectional view ofthe prefabricated frame 302 suitable for use in this embodiment. Theillustrated frame 302 includes a Kovar alloy core 702, or a core ofdifferent metal or alloy, overlaid with a first metallic layer 704 ofnickel which, in turn, is overlaid by an outer layer 706 of gold. Theuse of Kovar alloy for the core 702 of the frame 302 may be preferredwhere hard glass, e.g., Corning 7056 or 7058, is used for the sheet 304and where Kovar alloy or a similar material is used for the package base104, since these materials have a CTE for the temperature range 30° C.to 300° C. that is within the range from about 5.0-10⁻⁶/° K to about5.6-10⁻⁶/° K (e.g., from about 5.0 to about 5.6 ppm/° K).

Referring still to FIG. 7, another step of the manufacturing process isthe preparation of a prefabricated frame 302 for joining to the sheet304. As previously described, the frame 302 includes a continuoussidewall 306, which defines an aperture 308 therethrough. The sidewall306 includes a frame seal-ring area 310 on its upper surface and a baseseal-ring area 320 on its lower surface. The frame seal-ring area 310 isgenerally dimensioned to conform with the sheet seal-ring area 318 ofthe transparent sheet 304, while the base seal-ring area 320 isgenerally dimensioned to conform against the corresponding seal area onthe package base. The frame 302 may be manufactured using variousconventional metal forming technologies, including stamping, casting,die casting, extrusion/parting, and machining. It is contemplated thatstamping or die casting may be the most cost effective method forproducing the frames 302. However, fabricating the frame 302 usingphoto-chemical machining (PCM), also known as chemical etching, may, insome instances be the most economical method. In some instances, severalsheets of photo-chemical machined (i.e., etched) metals and/or alloymight be bonded together to form the frame 302. One of the bondingmethods includes TC bonding, also known as diffusion bonding, the PCM'dlayers together to create the frame 302. Depending upon the degree offlatness required for the contemplated bonding procedure and the degreeachieved by a particular frame manufacturing method, surface grinding,and possibly even lapping or polishing, may be required on the frameseal-ring area 310 or base seal-ring area 320, to provide the finalflatness necessary for a successful hermetic seal.

In this example, the base seal-ring area 320 is on the frame faceopposite frame seal-ring area 310, and may utilize the same layers ofnickel 704 overlaid by gold 706 to facilitate eventual welding to thepackage base 104. In some instances, the gold 706 will not be overlaidon the nickel 704.

In some embodiments, the frame 302 will serve as a “heat sink” and/or“heat spreader” when the cover assembly 300 is eventually welded to thepackage base 104. It is contemplated that conventional high temperaturewelding processes (e.g., manual or automatic electrical resistance seamwelding or laser welding) may be used for this operation. If themetallized glass sheet 304 were welded directly to the package base 104using these welding processes, the concentrated heat could cause thermalstresses likely to crack the glass sheet or distort its opticalproperties. However, when a metal frame is attached to the transparentsheet, it acts as both a heat sink, absorbing some of the heat ofwelding, and as a heat spreader, distributing the heat over a wider areasuch that the thermal stress on the transparent sheet 304 is reduced tominimize the likelihood of cracking or optical distortion. Kovar alloyis especially useful in this heat sink and heat spreading role asexplained by Kovar alloy's thermal conductivity, 0.0395, which isapproximately fourteen times higher than the thermal conductivity ofCorning 7052 glass, 0.0028.

Another important aspect of the frame 302 is that it should be formedfrom a material having a CTE that is similar to the CTE of thetransparent sheet 304 and the CTE of the package base 104. This matchingof CTE between the frame 302, transparent sheet 304 and package base 104is beneficial to minimize stresses between these components after theyare joined to one another so as to ensure the long term reliability ofthe hermetic seal therebetween under conditions of thermal cyclingand/or thermal shock environments.

For window assemblies that will be attached to package bases formed ofceramic, alumina or Kovar alloy, Kovar alloy is preferred for use as thematerial for the frame 304. Although Kovar alloy will be used for theframes in many of the embodiments discussed in detail herein, it will beunderstood that Kovar alloy is not necessarily suitable for use with alltransparent sheet materials. Additionally, other frame materials besidesKovar alloy may be suitable for use with glass. Suitability isdetermined by the desire that the material of the transparent sheet 304,the material of the frame 302 and the material of the package base 104all have closely matching CTEs to insure maximum long-term reliabilityof the hermetic seals.

Referring now to FIG. 8, the next step of the manufacturing process isto position the frame 302 against the sheet 304 such that at least aportion of the frame seal-ring area 310 and a least a portion of thesheet seal-ring area 318 contact one another along a continuous junctionregion 804 that circumscribes the window portion 312. Actually, in somecases a plasma-cleaning operation and/or a solvent or detergent cleaningoperation is performed on the seal-ring areas and any other sealingsurfaces just prior to joining the components to ensure maximumreliability of the joint. In FIG. 8, the sheet 304 moves from itsoriginal position (denoted in broken lines) until it is in contact withthe frame 302. It is, of course, first necessary to remove any remainingtacky tape or other masking materials left over from operations used toprepare the sheet seal-ring area 318 if they cannot withstand theelevated temperatures encountered in the joining process withoutdegradation of the mask material and/or its adhesive, if an adhesive isused to attach the mask to the sheet. It will be appreciated that it isnot necessary that the sheet seal-ring area 318 and the frame seal-ringarea 310 have an exact correspondence with regard to their entire areas,rather, it is only necessary that there be some correspondence betweenthe two seal-ring areas forming a continuous junction region 804, whichcircumscribes the window portion 312. In the embodiment illustrated inFIG. 8, the metallized layers 610 in the sheet seal-ring area 318 aremuch wider than the plated outer layer 706 of the frame seal-ring area310. Further, the window portion 312 of the sheet 304 extends partwaythrough the frame aperture 308, providing a means to center the sheet304 on the frame 302.

The next step of the manufacturing process is to heat the junctionregion 804 until a joint is formed between the frame 302 and the sheet304 all along the junction region, whereby a hermetic sealcircumscribing the window portion 312 is formed. It is necessary thatduring the step of heating the junction region 804, the temperature ofthe window portion 312 of the sheet 304 remain below its glasstransition temperature, T_(G) as well as below the softening temperatureof the sheet 304, to prevent damage to the finished surfaces 314 and316. The softening point for glass is defined as the temperature atwhich the glass has a viscosity of 107.6 dPa s or 107.6 poise (method ofmeasurement: ISO 7884-3). The current invention contemplates severaloptions for accomplishing this heating. A first option is to utilizethermal compression (TC) bonding, also known as diffusion bonding,including conventional hot press bonding as well as Hot Isostatic Pressor Hot Isostatic Processing (HIP) diffusion bonding. As previouslydescribed, TC bonding, also known as diffusion bonding involves theapplication of high pressures to the materials being joined such that areduced temperature is required to produce the necessary diffusion bond.Rules for determining the thickness and composition of the metalliclayers 610 on the sheet 304 were previously provided, for TC bonding to,e.g., a Kovar alloy, nickel or gold frame such as illustrated in FIG. 7.The estimated process parameters for the TC bonding of a Kovaralloy/nickel/gold frame 302 to a metallized sheet 304 having aluminum asthe final layer would be a temperature of approximately 380° C. at anapplied pressure of approximately 95,500 psi (6713.65 kg/cm²). Underthese conditions, the gold plating 706 on the Kovar alloy frame 302 willdiffuse into/with the aluminum layer, e.g., layer 4 in Example 7. Sincethe 380° C. temperature necessary for TC bonding is below theapproximately 500° C. to 900° C. T_(G) for hard glasses such as Corning7056, the TC bonding process could be performed in a single or batchmode by fixturing the cover assembly components 302, 304 together incompression and placing the compressed assemblies into a furnace (oroven, etc.) at approximately 380° C. The hermetic bond would be obtainedwithout risking the finished surfaces 314 and 316 of the window portion312. Vacuum, sometimes with some small amounts of specific gassesincluded, or other atmospheres with negative or positive pressures mightbe needed inside the furnace to promote the TC bonding process.

Alternatively, employing resistance welding at the junction area 804 toadd additional heat in addition to the TC bonding could allow preheatingthe window assemblies to less than 380° C. and possibly reduce theoverall bonding process time. In another method, the TC bonding could beaccomplished by fixturing the cover assembly components 302 and 304using heated tooling that would heat the junction area 304 byconduction. In yet another alternative method, electrical resistancewelding can be used to supply 100% of the heat required to achieve thenecessary TC bonding temperature, thereby eliminating the need forfurnaces, ovens, etc. or specialized thermally conductive tooling.

After completion of TC bonding or other welding processes, the windowassembly 300 is ready for final processing, for example, chamfering theedges of the cover assembly to smooth them and prevent chipping,scratching, marking, etc., during post-assembly, cleaning, marking orother operations. In some instances, the final processing may includethe application of a variety of coatings to the window and/or to theframe.

Referring now to FIG. 9, there is illustrated a block diagram of themanufacturing process just described in accordance with one embodimentof the current invention. Block 902 represents the step of obtaining asheet of transparent material, e.g., glass or other material, havingfinished top and bottom surfaces as previously described. The processthen proceeds to block 904 as indicated by the arrow.

Block 904 represents the step of applying surface treatments to thesheet, e.g., scratch-resistant or anti-reflective coatings, aspreviously described. In addition to these permanent surface treatments,block 904 also represents the sub-steps of applying tape or othertemporary masks to the surfaces of the sheet to protect them during thesubsequent steps of the process. It will be appreciated that the stepsrepresented by block 904 are optional and that one or more of thesesteps may not be present in every embodiment of the invention. Theprocess then proceeds to block 906 as indicated by the arrow.

Block 906 represents the step of preparing the seal-ring area on thesheet to provide better adhesion for the metallic layers, if suchmetallic layers are used. This step usually involves roughening theseal-ring area using chemical etching, mechanical grinding, laserablating or sandblasting as previously described. To the extentnecessary, block 906 also represents the sub-steps of removing anymasking material from the seal-ring area. Block 906 further representsthe optional steps of cleaning the sheet (or at least the seal-ring areaof the sheet) to remove any greases, oils or other contaminants from thesurface of the sheet. As previously discussed, such cleaning steps maybe performed regardless of whether the seal-ring area is to bemetallized (i.e., to promote better adhesion of the metallic layers) oris to be left unmetallized (i.e., to promote better diffusion bonding ofthe unmetallized sheet). It will be appreciated that the stepsrepresented by block 906 are optional and that some or all of thesesteps may not be present in every embodiment of the invention. Theprocess then proceeds to block 908 as indicated by the arrow.

Block 908 represents the step of metallizing the seal-ring areas of thesheet. The step represented by block 908 is mandatory only when thedesired bond of sheet 304 to frame 302 is a metal-to-metal bond since atleast one metallic layer must be applied to the seal-ring area of thesheet. It is possible, for instance by use of diffusion bondingprocesses, to bond the sheet 304 to frame 302 without first metallizingsheet 304. In most embodiments, block 908 will represent numeroussub-steps for applying successive metallic layers to the sheet, wherethe layers of each sub-step may be applied by processes including CVD,PVD, cold-spray or solution bath plating as previously described.Following the steps represented by block 908, the sheet is ready forjoining to the frame. However, before the process can proceed to thisjoining step (i.e., block 916), a suitable frame must first be prepared.

Block 910 represents the step of obtaining a pre-fabricated frame,preferably having a CTE that closely matches the CTE of the transparentsheet from block 902 and the CTE of the package base. In most caseswhere the base is alumina or Kovar alloy, a frame formed of Kovar alloywill be suitable. As previously described, the frame may be formedusing, e.g., stamping, die-casting or other known metal-formingprocesses. The process then proceeds to block 912 as indicated by thearrow.

Block 912 represents the step of grinding, polishing and/or otherwiseflattening the seal-ring areas of the frame as necessary to increase itsflatness so that it will fit closely against the seal-ring areas of thetransparent sheet. It will be appreciated that the steps represented byblock 912 are optional and may not be necessary or present in everyembodiment of the invention. The process then proceeds to block 914 asindicated by the arrow.

Block 914 represents the step of applying additional metallic layers tothe seal-ring areas of the frame. These metallic layers are sometimesnecessary to achieve compatible chemistry for bonding with themetallized seal-ring areas of the transparent sheet. In mostembodiments, block 914 will represent numerous sub-steps for applyingsuccessive metallic layers to the frame. Block 914 further representsthe optional steps of cleaning the frame (or at least the seal-ring areaof the frame) to remove any greases, oils or other contaminants from thesurface of the frame. As previously discussed, such cleaning steps maybe performed regardless of whether the seal-ring area of the frame is tobe metallized with additional metal layers or is to be used withoutadditional metallization. Once the steps represented by block 914 arecompleted, the frame is ready for joining to the transparent sheet.Thus, the results of process block 908 and block 914 both proceed toblock 916 as indicated by the arrows.

Block 916 represents the step of clamping the prepared frame togetherwith the prepared transparent sheet so that their respective metallizedseal-ring areas are in contact with one another under conditionsproducing a predetermined contact pressure at the junction regioncircumscribing the window portion. This predetermined contact pressurebetween the seal-ring surfaces allows thermal compression (TC) bondingof the metallized surfaces to occur at a lower temperature than would berequired for conventional welding (including most soldering and brazingprocesses). The process then proceeds to block 918 as indicated by thearrow.

Block 918 represents the step of applying heat to the junction betweenthe frame and the transparent sheet while maintaining the predeterminedcontact pressure until the temperature is sufficient to cause thermalcompression bonding to occur. In some embodiments, block 918 willrepresent a single heating step, e.g., heating the fixtured assembly ina furnace. In other embodiments, block 918 will represent severalsub-steps for applying heat to the junction area, for example, firstpreheating the fixtured assembly (e.g., in a furnace) to an intermediatetemperature, and then using resistance welding techniques along thejunction to raise the temperature of the localized area of the metalliclayers the rest of the way to the temperature where thermal compressionbonding will occur. The thermal compression bonding creates a hermeticseal between the transparent sheet material and the frame. The processthen proceeds to block 920 as indicated by the arrow.

In the illustrated example, metallized seal-ring areas are joined usingdiffusion bonding/thermal compression bonding in which the predeterminedpressure is applied first (block 916) and the heat is applied second(block 918). It will be appreciated, however, that the use of diffusionbonding is not limited to these specific conditions. In some otherembodiments, the sheet and/or frame may not be metallized prior tobonding. In still other embodiments, the heat may be applied first untilthe desired bonding temperature is reached, and the predeterminedpressure may be applied thereafter until the diffusion bond is formed.In yet additional embodiments, the heat and pressure may be appliedsimultaneously until the diffusion bond is formed.

Block 920 represents the step of completing the window assembly. Block920 may represent merely cooling the window assembly after thermalcompression bonding, or it may represent additional finishing processesincluding chamfering the edges of the assembly to prevent chipping,cracking, etc., marking the assembly, coating the window and/or theframe with one or more materials, or other post-assembly procedures. Theprocess of this embodiment has thus been described.

It will be appreciated that in alternative embodiments of the invention,conventional welding techniques (including soldering and/or brazing) maybe used instead of thermal compression bonding to join the frame to thetransparent sheet. In such alternative embodiments, the stepsrepresented by blocks 916 and 918 of FIG. 9 would be replaced by thesteps of fixturing the frame and transparent sheet together so that themetallized seal-ring areas are in contact with one another (but notnecessarily producing a predetermined contact pressure along thejunction) and then applying heat to the junction area using conventionalmeans until the temperature is sufficient to cause the melting anddiffusing of the metallic layers necessary to achieve the welded bond.

In an alternative embodiment, braze-soldering is used to join the frame302 to the metallized sheet 304. In this embodiment, a solder metal orsolder alloy may be utilized as the final layer of the metallic layers610 on the metallized sheet 304, and clamping the sheet 304 to the frame302 at a high predetermined contact pressure is not required. A soldermetal or solder alloy preform may be utilized as a separate,intermediate item between the frame 302 and the sheet 304 instead ofhaving a solder metal or solder alloy as the final layer of the metalliclayers 610 on the metallized sheet 304. Light to moderate clampingpressure can be used: 1) to insure alignment during the solder's moltenphase; and 2) to promote even distribution of the molten solder allalong the junction region between the respective seal-ring areas;thereby helping to insure a hermetic seal, however, this clampingpressure does not contribute to the bonding process itself as in TCbonding. In most other respects, however, this embodiment issubstantially similar to that previously described.

The following examples, not to be considered limiting, are provided toillustrate the details of the metallic layers 610 in the sheet seal-ringarea 318 that are suitable for braze-soldering to a Kovaralloy/nickel/gold frame 302 such as that illustrated in FIG. 7.

Example 33

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD0.002 25 2 Cu CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Eutectic Au—Sn CVD, PVD, SBP 1.27 127 solder

Example 34

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD0.002 25 2 Cu CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Sn—Bi solder CVD, PVD, SBP 1.27 152.4

Example 35

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD0.002 25 2 Zn CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Eutectic Au—Sn CVD, PVD, SBP 1.27 127 solder

Example 36

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD0.002 25 2 Zn CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Sn—Bi solder CVD, PVD, SBP 1.27 152.4

Example 37

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15 2 Zn CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Eutectic Au—Sn CVD, PVD, SBP 1.27 127 solder

Example 38

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15 2 Ni CVD, PVD, SBP 0.002 6.35 3 Eutectic Au—Sn CVD, PVD, SBP1.27 127 solder

Example 39

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15 2 Zn CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Sn—Bi solder CVD, PVD, SBP 1.27 152.4

Example 40

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15 2 Ni CVD, PVD, SBP 0.002 6.35 3 Sn—Bi solder CVD, PVD, SBP1.27 152.4

Example 41

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15 2 Sn—Bi solder CVD, PVD, SBP 1.27 152.4

Example 42

Min. Max. Layers Metal Deposition (microns) (microns) 1 De-stressed SnCVD, PVD 1.27 152.4 Solder

Example 43

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn—Bi SolderCVD, PVD 1.27 152.4

Example 44

Min. Max. Layers Metal Deposition (microns) (microns) 1 Eutectic Au—SnCVD, PVD 1.27 127 Solder

Example 45

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD0.002 152.4 2 Eutectic Au—Sn CVD, PVD, SBP 1.27 127 Solder

Example 46

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD0.002 152.4 2 Sn—Bi Solder CVD, PVD, SBP 1.27 152.4

While numerous examples herein show the use of eutectic Au—Sn, otherapplications may utilize non-eutectic Au—Sn, or other eutectic ornon-eutectic solders for attaching the window. This allows subsequentuse of a higher melting temperature solder to attach the unit to ahigher level assembly without melting the window bond.

By way of further examples, not to be considered limiting, the followingcombinations are preferred for the metallic layers 610 in the sheetseal-ring area 318 for braze-soldering to a Kovar alloy/nickel/goldframe 302 such as that illustrated in FIG. 7.

Example 47

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD 0.12.54 2 Cu CVD, PVD, SBP 0.25 2.54 3 Ni CVD, PVD, SBP 1 5.08 4 EutecticAu—Sn CVD, PVD, SBP 2.54 63.5 solder

Example 47a

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD 0.12.54 2 Cu CVD, PVD, SBP 0.25 2.54 3 Ni CVD, PVD, SBP 1 5.08 4 Sn—Cu—AgSolder CVD, PVD, SBP 2.54 63.5

Example 48

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD 0.12.54 2 Cu CVD, PVD, SBP 0.25 2.54 3 Ni CVD, PVD, SBP 1 5.08 4 Sn—Bisolder CVD, PVD, SBP 2.54 127

Example 49

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD 0.12.54 2 Zn CVD, PVD, SBP 0.3175 5.08 3 Ni CVD, PVD, SBP 1 5.08 4 EutecticAu—Sn CVD, PVD, SBP 2.54 63.5 solder

Example 49a

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD 0.12.54 2 Zn CVD, PVD, SBP 0.3175 5.08 3 Ni CVD, PVD, SBP 1 5.08 4 Sn—Cu—AgSolder CVD, PVD, SBP 2.54 63.5

Example 50

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD 0.12.54 2 Zn CVD, PVD, SBP 0.3175 5.08 3 Ni CVD, PVD, SBP 1 5.08 4 Sn—Bisolder CVD, PVD, SBP 2.54 127

Example 51

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Zn CVD, PVD, SBP 0.3175 5.08 3 Ni CVD, PVD, SBP 1 5.08 4 EutecticAu—Sn CVD, PVD, SBP 2.54 63.5 solder

Example 51a

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Zn CVD, PVD, SBP 0.3175 5.08 3 Ni CVD, PVD, SBP 1 5.08 4 Sn—Cu—AgSolder CVD, PVD, SBP 2.54 63.5

Example 52

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Ni CVD, PVD, SBP 1 5.08 3 Eutectic Au—Sn CVD, PVD, SBP 2.54 63.5solder

Example 52a

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Ni CVD, PVD, SBP 1 5.08 3 Sn—Cu—Ag Solder CVD, PVD, SBP 2.54 63.5

Example 53

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Zn CVD, PVD, SBP 0.3175 5.08 3 Ni CVD, PVD, SBP 1 5.08 4 Sn—Bisolder CVD, PVD, SBP 2.54 127

Example 54

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Ni CVD, PVD, SBP 1 5.08 3 Sn—Bi solder CVD, PVD, SBP 2.54 127

Example 55

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Sn—Bi solder CVD, PVD, SBP 2.54 127

Example 56

Min. Max. Layers Metal Deposition (microns) (microns) 1 De-stressed SnCVD, PVD 2.54 127 Solder

Example 57

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn—Bi SolderCVD, PVD 2.54 127

Example 58

Min. Max. Layers Metal Deposition (microns) (microns) 1 Eutectic Au—SnCVD, PVD 2.54 63.5 Solder

Example 58a

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn—Cu—Ag SolderCVD, PVD 2.54 63.5

Example 59

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD 0.15.08 2 Eutectic Au—Sn CVD, PVD, SBP 2.54 63.5 Solder

Example 59a

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD 0.15.08 2 Sn—Cu—Ag Solder CVD, PVD, SBP 2.54 63.5

Example 60

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD 0.15.08 2 Sn—Bi Solder CVD, PVD, SBP 2.54 127

Referring now to FIG. 10, there is illustrated yet another embodiment ofthe current invention. Note that in this embodiment, the cover assembly300 is circular in configuration rather than rectangular. It will beappreciated that this is simply another possible configuration for acover assembly manufactured in accordance with this invention, and thatthis embodiment is not limited to configurations of any particularshape. As in the embodiment previously described, this embodiment alsouses braze-soldering to hermetically join the transparent sheet 304 tothe frame 302. However, in this embodiment, the solder for brazesoldering is provided in the form of a separate solder preform 1000having the shape of the sheet seal-ring area 318 or the frame seal-ringarea 310. Also in this embodiment, preform 1000 can be of materialsother than solder for use as an innerlayer or interlayer materialbetween the transparent sheet 304 and the frame 302. When used as theinnerlayer or interlayer for TC bonding, one or more elements of preform1000 diffuses with one or more elements of sheet 304 and the frame 302.

In this embodiment, when the preform solder 1000 is used forbraze-soldering to hermetically join the transparent sheet 304 to theframe 302, instead of positioning the frame and the sheet directlyagainst one another, the frame 302 and the sheet 304 are insteadpositioned against opposite sides of the solder preform 1000 such thatthe solder preform is interposed between the frame seal-ring area 310and the sheet seal-ring are 318 along a continuous junction region thatcircumscribes the window portion 312. After the frame 302 and sheet 304are positioned against the solder preform 1000, the junction region isheated until the solder preform fuses forming a solder joint between theframe and sheet all along the junction region. The heating of thejunction region may be performed by any of the procedures previouslydescribed, including heating or preheating in a furnace, oven, etc.,either alone or in combination with other heating methods includingresistance welding. It is required that during the step of heating thejunction region, the temperature of the window portion 312 of the sheet304 remain below the glass transition temperature T_(G) and thesoftening temperature such that the finished surfaces 314 and 316 on thesheet are not adversely affected.

The current embodiment using a solder preform 1000 can be used forjoining a metallized sheet 304 to a Kovar alloy/nickel/gold frame suchas that illustrated in FIG. 7. In accordance with a preferredembodiment, the solder preform 1000 is formed of a gold-tin (Au—Sn)alloy, and in a more preferred embodiment, the gold-tin alloy is theeutectic composition. One of the alternative alloys for preform 1000 istin-copper-silver (Sn—Cu—Ag). The thickness of the gold-tin preform 1000will probably be within the range from about 6 microns to about 101.2microns. The thickness of other alloys for preform 1000 will alsoprobably be within the range of about 6 microns to about 101.2 microns.

The following examples, not to be considered limiting, are provided toillustrate the details of the metallic layers 610 and the sheetseal-ring area 318 that are suitable for braze-soldering to a Kovaralloy/nickel/gold frame in combination with a gold-tin solder preform orother suitable solder alloy preforms, including, but not limited totin-copper-silver alloys.

Example 61

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD0.002 25 2 Cu CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Au CVD, PVD, SBP 0.0508 0.508

Example 62

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD0.002 25 2 Cu CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Sn—Bi CVD, PVD, SBP 0.635 12.7

Example 63

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD0.002 25 2 Zn CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Au CVD, PVD, SBP 0.0508 0.508

Example 64

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD0.002 25 2 Zn CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Sn—Bi CVD, PVD, SBP 0.635 12.7

Example 65

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15 2 Zn CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Au CVD, PVD, SBP 0.0508 0.508

Example 66

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15 2 Ni CVD, PVD, SBP 0.002 6.35 3 Au CVD, PVD, SBP 0.0508 0.508

Example 67

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15 2 Zn CVD, PVD, SBP 0.002 6.35 3 Ni CVD, PVD, SBP 0.002 6.35 4Sn—Bi CVD, PVD, SBP 0.635 12.7

Example 68

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15 2 Ni CVD, PVD, SBP 0.002 6.35 3 Sn—Bi CVD, PVD, SBP 0.63512.7

Example 69

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15 2 Sn—Bi CVD, PVD, SBP 0.635 12.7

Example 70

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD0.002 0.15

Example 71

Min. Max. Layers Metal Deposition (microns) (microns) 1 De-stressed SnCVD, PVD 0.635 12.7 or Sn—Bi

Example 72

Min. Max. Layers Metal Deposition (microns) (microns) 1 Au CVD, PVD0.0508 0.508

Example 73

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD0.002 152.4 2 Au CVD, PVD, SBP 0.0508 0.508

Example 74

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD0.002 152.4 2 Sn—Bi CVD, PVD, SBP 0.635 12.7

Example 75

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD0.002 152.4 2 Sn (De-stressed CVD, PVD, SBP 0.635 12.7 after deposition)

By way of further examples, not to be considered limiting, the followingcombinations are preferred for the metallic layers 610 and the sheetseal-ring area 318 for braze-soldering to a Kovar alloy/nickel/goldframe in combination with a gold-tin soldered preform. In addition tohaving a frame of Kovar alloy/nickel/gold, materials other than Kovarmay be employed as the frame's base material and the overlying layer orlayers may be nickel without the gold, or combinations of two or moremetals including, but not limited to nickel and gold.

Example 76

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD 0.12.54 2 Cu CVD, PVD, SBP 0.25 2.54 3 Ni CVD, PVD, SBP 1 5.08 4 Au CVD,PVD, SBP 0.127 0.381

Example 77

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD 0.12.54 2 Cu CVD, PVD, SBP 0.25 2.54 3 Ni CVD, PVD, SBP 1 5.08 4 Sn—Bi CVD,PVD, SBP 2.54 7.62

Example 78

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD 0.12.54 2 Zn CVD, PVD, SBP 0.3175 5.08 3 Ni CVD, PVD, SBP 1 5.08 4 Au CVD,PVD, SBP 0.127 0.381

Example 79

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al CVD, PVD 0.12.54 2 Zn CVD, PVD, SBP 0.3175 5.08 3 Ni CVD, PVD, SBP 1 5.08 4 Sn—BiCVD, PVD, SBP 2.54 7.62

Example 80

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Zn CVD, PVD, SBP 0.3175 5.08 3 Ni CVD, PVD, SBP 1 5.08 4 Au CVD,PVD, SBP 0.127 0.381

Example 81

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Ni CVD, PVD, SBP 1 5.08 3 Au CVD, PVD, SBP 0.127 0.381

Example 82

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Zn CVD, PVD, SBP 0.3175 5.08 3 Ni CVD, PVD, SBP 1 5.08 4 Sn—BiCVD, PVD, SBP 2.54 7.62

Example 83

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Ni CVD, PVD, SBP 1 5.08 3 Sn—Bi CVD, PVD, SBP 2.54 7.62

Example 84

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12 2 Sn—Bi CVD, PVD, SBP 2.54 7.62

Example 85

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr CVD, PVD 0.050.12

Example 86

Min. Max. Layers Metal Deposition (microns) (microns) 1 De-stressed SnCVD, PVD 2.54 7.62 or Sn—Bi

Example 87

Min. Max. Layers Metal Deposition (microns) (microns) 1 Au CVD, PVD0.127 0.381

Example 88

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD 0.15.08 2 Au CVD, PVD, SBP 0.127 0.381

Example 89

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD 0.15.08 2 Sn—Bi CVD, PVD, SBP 2.54 7.62

Example 90

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni CVD, PVD 0.15.08 2 Sn (De-stressed CVD, PVD, SBP 2.54 7.62 after deposition)

Referring now to FIG. 11, there is illustrated yet another embodiment ofthe current invention. This embodiment also uses soldering, however, inthis embodiment the solder is applied via inkjet technology to eitherthe metallized area 610 in the sheet seal-ring area 318 or the sheetseal-ring 310 of the frame assembly. FIG. 11 shows a portion of theKovar alloy/nickel/gold frame 302 (or other frame alloy and overlayercombination) and an inkjet dispensing head 1102 which is dispensingoverlapping drops of solder 1104 onto the frame seal-ring area 310 asthe dispensing head moves around the frame aperture 308 or the frameaperture is moved underneath the dispensing head, as indicated by arrow1106. Preferably, the inkjet dispensed solder is a gold-tin (Au—Sn)alloy, and more preferably it is the eutectic composition. The preferredthickness of the gold-tin solder applied by dispensing head 1102 in thisembodiment is within the range from about 6 microns to about 101.2microns. It will be appreciated that while the example illustrated inFIG. 11 shows the dispensing head 1102 depositing the solder droplets1104 onto the frame 302, in other embodiments the inkjet depositedsolder may be applied to the sheet seal-ring area 318, either alone orin combination with applications on the frame seal-ring area 310. Instill other embodiments, the inkjet deposited solder may be used tocreate a discrete solder preform that would be employed as described inthe previous examples herein. In still other embodiments, the inkjetdeposited material, which may or may not be solder, may be used tocreate an innerlayer or interlay preform that would be employed for usein TC bonding or HIP diffusion bonding as described in previous examplesherein. Details of the metallic layers 610 in the sheet seal-ring area318 that are suitable for a soldering to a Kovar alloy/nickel/gold frame302 such as that illustrated in FIG. 7 using inkjet supplied solder aresubstantially identical to those layers illustrated in previous Examples21 through 32.

Referring now to FIGS. 12 a through 12 c and FIGS. 13 a through 13 c,there is illustrated yet another alternative method for manufacturingcover assemblies constituting another embodiment of the currentinvention. Whereas, in the previous embodiments a separate prefabricatedmetal frame was joined to the transparent sheet to act as a heatspreader/heat sink needed for subsequent welding, in this embodiment acold gas dynamic spray deposition process is used to fabricate ametallic frame/heat spreader directly on the transparent sheet material.In other words, in this embodiment the frame is fabricated directly onthe transparent sheet as an integral part, no subsequent joiningoperation is required. In addition, since cold gas dynamic spraydeposition can be accomplished at near room temperature, this method isespecially useful where the transparent sheet material and/or surfacetreatments thereto have a relatively low T_(G), melting temperature, orother heat tolerance parameter.

Referring specifically to FIG. 12 a, there is illustrated a sheet oftransparent material 304 having a window portion 312 defined thereupon.The window portion 312 has finished top and bottom surfaces 314 and 316(note that the 304 sheet appears bottom side up in FIGS. 12 a through 12c). A frame attachment area 1200 is defined on the sheet 304, the frameattachment area circumscribing the window portion 312. It will beappreciated in the embodiment illustrated in FIGS. 12 a-c that the frameattachment area 1200 need not follow the specific boundaries of thewindow area 312 (i.e., which in this case are circular) as long as theframe attachment area 1200 completely circumscribes the window portion.

It will be appreciated that, unless specifically noted otherwise, theinitial steps of obtaining a transparent sheet having a window portionwith finished top and bottom surfaces, preparing the seal-ring area ofthe sheet and metallizing the seal-ring area of the sheet aresubstantially identical to those described for the previous embodimentsand will not be described in detail again.

Referring now also to FIG. 13 a, there is illustrated a partialcross-sectional view to the edge of the sheet 304. In this example, thestep of preparing a frame attachment area 1200 on the sheet 304comprises an optional step of roughening the frame attachment area byroughening and/or grinding the surface from its original level (shown inbroken line) to produce a recessed area 1302. After the frame attachmentarea 1200 has been prepared, metal layers are deposited into the frameattachment area of the sheet using cold gas dynamic spray deposition. InFIG. 12 b, an initial metal layer 1202 has been applied into the frameattachment area 1200 using cold gas dynamic spray deposition.

Referring now also to FIG. 13 b, the cold gas dynamic spray nozzle 1304is shown depositing a stream of metal particles 1306 onto the frameattachment area 1200. The initial layer 1202 has now been overlaid witha secondary layer 1204 and the spray nozzle 1304 is shown as it beginsto deposit the final Kovar alloy layer 1206. Layer 1206 need not beKovar.

Referring now to FIGS. 12 c and 13 c, the completed cover assembly 1210is illustrated including the integral frame/heat spreader 1212, whichhas been built up from layer 1206 to a predetermined height, denoted byreference numeral 1308, above the finished surface of the sheet. In apreferred embodiment, the predetermined height 1308 of the built-upmetal frame above the frame attachment area 1200 is within the rangefrom about 5% to about 100% of the thickness denoted by referencenumeral 1310 of the sheet 304 beneath the frame attachment area. In theembodiment shown, the step of depositing metal using cold gas dynamicspray included depositing a layer of Kovar alloy onto the sheet tofabricate the built-up frame/heat spreader 1212. The use of cold gasdynamic spray deposition allows a tremendous range of thickness for thisKovar alloy layer, which thickness may be within the range from about2.54 microns to about 12,700 microns. It will, of course, be appreciatedthat the frame/heat spreader 1212 may be fabricated through thedeposition of materials other than Kovar alloy, depending upon thecharacteristics of the transparent sheet 304 and of the package base104, especially their respective CTEs.

The following examples, not to be considered limiting, are provided toillustrate the details of the metallic layers, denoted collectively byreference numeral 1207 for forming a frame/heat spreader compatible withhard glass transparent sheets and Kovar alloy or ceramic package bases.The deposition of materials other than Kovar alloy may be used as thefinal layer whenever Kovar Alloy is indicated as the final layer,depending upon the characteristics of the transparent sheet 304 and ofthe package base 104, especially their respective CTEs.

Example 91

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al cold gasspray 2.54 127 2 Cu cold gas spray 2.54 127 3 Ni cold gas spray 2.54 1274 Kovar Alloy cold gas spray 127 12,700

Example 92

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al cold gasspray 2.54 127 2 Ni cold gas spray 2.54 127 3 Kovar Alloy cold gas spray127 12,700

Example 93

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al cold gasspray 2.54 127 2 Kovar Alloy cold gas spray 127 12,700

Example 94

Min. Max. Layers Metal Deposition (microns) (microns) 1 Kovar Alloy coldgas spray 127 12,700

Example 95

Min. Max. Layers Metal Deposition (microns) (microns) 1 Zn cold gasspray 2.54 127 2 Ni cold gas spray 2.54 127 3 Kovar alloy cold gas spray127 12,700

Example 96

Min. Max. Layers Metal Deposition (microns) (microns) 1 Zn cold gasspray 2.54 127 2 Kovar alloy cold gas spray 127 12,700

Example 97

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr cold gasspray 2.54 127 2 Ni cold gas spray 2.54 127 3 Kovar alloy cold gas spray127 12,700

Example 98

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr cold gasspray 2.54 127 2 Kovar alloy cold gas spray 127 12,700

Example 99

Min. Max. Layers Metal Deposition (microns) (microns) 1 A1 cold gasspray 2.54 127 2 Zn cold gas spray 2.54 127 3 Ni cold gas spray 2.54 1274 Kovar Alloy cold gas spray 127 12,700

Example 100

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni cold gasspray 2.54 127 2 Kovar Alloy cold gas spray 127 12,700

Example 101

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn or Sn—Bi coldgas spray 2.54 127 2 Zn cold gas spray 2.54 127 3 Ni cold gas spray 2.54127 4 Kovar Alloy cold gas spray 127 12,700

Example 102

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn or Sn—Bi coldgas spray 2.54 127 2 Ni cold gas spray 2.54 127 3 Kovar Alloy cold gasspray 127 12,700

By way of further examples, not to be considered limiting, the followingcombinations are preferred for the metallic layers 1207 for forming aframe/heat spreader compatible with hard glass transparent sheets andKovar or other alloys or ceramic package bases. The deposition ofmaterials other than Kovar alloy may be used as the final layer wheneverKovar Alloy is indicated as the final layer, depending upon thecharacteristics of the transparent sheet 304 and of the package base104, especially their respective CTEs.

Example 103

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al cold gasspray 12.7 76.2 2 Cu cold gas spray 12.7 76.2 3 Ni cold gas spray 12.776.2 4 Kovar Alloy cold gas spray 635 2,540

Example 104

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al cold gasspray 12.7 76.2 2 Ni cold gas spray 12.7 76.2 3 Kovar Alloy cold gasspray 635 2,540

Example 105

Min. Max. Layers Metal Deposition (microns) (microns) 1 Al cold gasspray 12.7 76.2 2 Kovar Alloy cold gas spray 635 2,540

Example 106

Min. Max. Layers Metal Deposition (microns) (microns) 1 Kovar Alloy coldgas spray 635 2,540

Example 107

Min. Max. Layers Metal Deposition (microns) (microns) 1 Zn cold gasspray 12.7 76.2 2 Ni cold gas spray 12.7 76.2 3 Kovar alloy cold gasspray 635 2,540

Example 108

Min. Max. Layers Metal Deposition (microns) (microns) 1 Zn cold gasspray 12.7 76.2 2 Kovar alloy cold gas spray 635 2,540

Example 109

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr cold gasspray 12.7 76.2 2 Ni cold gas spray 12.7 76.2 3 Kovar alloy cold gasspray 635 2,540

Example 110

Min. Max. Layers Metal Deposition (microns) (microns) 1 Cr cold gasspray 12.7 76.2 2 Kovar alloy cold gas spray 635 2,540

Example 111

Min. Max. Layers Metal Deposition (microns) (microns) 1 A1 cold gasspray 12.7 76.2 2 Zn cold gas spray 12.7 76.2 3 Ni cold gas spray 12.776.2 4 Kovar Alloy cold gas spray 635 2,540

Example 112

Min. Max. Layers Metal Deposition (microns) (microns) 1 Ni cold gasspray 12.7 76.2 2 Kovar Alloy cold gas spray 635 2,540

Example 111

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn or Sn—Bi coldgas spray 12.7 76.2 2 Zn cold gas spray 12.7 76.2 3 Ni cold gas spray12.7 76.2 4 Kovar Alloy cold gas spray 635 2,540

Example 114

Min. Max. Layers Metal Deposition (microns) (microns) 1 Sn or Sn—Bi coldgas spray 12.7 76.2 2 Ni cold gas spray 12.7 76.2 3 Kovar Alloy cold gasspray 635 2,540

After the deposition of the metal layers using the cold gas dynamicspray deposition, it may be necessary to grind or shape the top surfaceof the built-up frame 1212 to a predetermined flatness before performingadditional steps to ensure that a good contact will be made in laterbonding. Another process which may be used, either alone or incombination with shaping the top surface of the built-up frame, is thedepositing of additional metal layers onto the built-up frame/heatspreader 1212 using solution bath plating. The most common reason forsuch plated layers is to promote a good bonding when the frame/heatspreader is adjoined to the package base 104. In a preferred embodiment,the additional metallic layers applied to the built-up frame 1212include a layer of nickel directly over the cold gas dynamic spraydeposited metal having a thickness within the range of about 0.002microns to about 25 microns and, in some instances, then solution bathplating a layer of gold over the nickel layer until the gold layer has athickness within the range from about 0.0508 microns to about 0.508microns.

Referring now to FIG. 14, there is illustrated a block diagram of thealternative embodiment utilizing cold gas dynamic spray deposition. Itwill be appreciated that, unless specifically noted otherwise, theinitial steps of obtaining a transparent sheet having finished surfaces,applying surface treatments to the sheet, cleaning, roughening orotherwise preparing the frame attachment area of the sheet aresubstantially identical to those described for the previous embodimentsand will not be described in detail again. For example, block 1402 ofFIG. 14 represents the step of obtaining a sheet of transparent materialhaving finished surfaces and corresponds directly with block 902, andwith the description of suitable transparent materials. Similarly,except as noted, blocks 1404, 1406 and 1408 of FIG. 14 corresponddirectly with blocks 904, 906 and 908, respectively, of FIG. 9 and withthe previous descriptions of the steps and sub-steps provided herein.Thus, it will be understood that all of the options described forperforming the various steps and sub-steps represented by the blocks902-908 in the previous (i.e., prefabricated frame) embodiments areapplicable to the blocks 1402-1408 in the current (i.e., cold spray)embodiment.

The next step of the process is to use cold gas dynamic spray depositionto deposit frame/heat spreader metal onto any previously deposited metallayers in the frame attachment area 1200. This step is represented byblock 1410. As previously described in connection with FIGS. 13 b and 13c, the high velocity particles 1306 from the gas nozzle 1304 form a newlayer on the previous metallic layers, and by directing the cold sprayjet across the frame attachment area 1200 repeatedly, the new materialcan become a continuous metallic layer around the entire periphery ofthe frame attachment area, i.e., it will circumscribe the window portion312 of the transparent sheet 304. Where the material of the package base104 (to which the cover assembly 1210 will eventually be joined) isKovar alloy or appropriately metallized alumina, Kovar alloy ispreferred for the material 1206 to be cold sprayed to form the integralframe. In other cases, a heat spreader material should be selected whichhas a CTE that is closely matched to the CTE of the package base 104. Ofcourse, that material must also be compatible with the cold gas dynamicspray process.

The cold spraying of the powdered heat spreader material is continueduntil the new layer 1206 reaches the thickness required to serve as aheat spreader/integral frame. This would represent the end of theprocess represented by block 1410. For some applications, the built-upheat spreader/frame 1212 is now complete and ready for use. For otherapplications, however, performing further finishing operations on theheat spreader/frame 1212 may be desirable.

For example, it is known that significant residual stresses may beencountered in metal structures deposited using cold-gas dynamic spraytechnology as a result of the mechanics of the spray process. Thesestresses may make the resulting structure prone to dimensional changes,cracking or other stress-related problems during later use. Annealing bycontrolled heating and cooling is known to reduce or eliminate residualstresses. Thus, in some applications, the integral heat spreader/frame1212 is annealed following its deposition on the sheet 304. Thisoptional step is represented by block 1411 in FIG. 14. In someembodiments, the annealing step 1411 may include the annealing of thetotality of the sprayed-on metals and alloys constituting the heatspreader/frame 1212. In other embodiments, however, the annealing step1411 includes annealing only the outermost portions of the integralbuilt-up heat spreader/frame 1212, while the inner layers are leftunannealed.

It will be appreciated that there are flatness requirements for thesealing surface at the “top” of the heat spreader (which is actuallyprojecting from the bottom surface 316 of the sheet). If these flatnessrequirements are not met via the application of the heat spreadermaterial by the cold spray process, it will be necessary to flatten thesealing surface at the next step of the process. This step isrepresented by block 1412 in FIG. 14. There are a number of options forachieving the required surface flatness. First, it is possible to removesurface material from the heat spreader to achieve the requiredflatness. This may be accomplished by conventional surface grinding, byother traditional mechanical means, or it may be accomplished by thelaser removal of high spots. Where material removal is used, care mustbe taken to avoid damaging the finished window surfaces 314 and 316during the material removal operations. Special fixturing and/or maskingof the window portion 312 may be required. Alternatively, if the coldspray deposited heat spreader 1212 is ductile enough, the surface may beflattened using a press operation, i.e., pressing the frame against aflat pattern or by employing a rolling operation. This would reduce thehandling precautions as compared to using a surface grinder or laseroperations.

Finally, as previously described, in some embodiments additional metallayers are plated onto the integral frame/heat spreader 1212. Theseoptional plating operations, such as solution bath plating layers ofnickel and gold onto a Kovar alloy frame, are represented by block 1414in FIG. 14. In the embodiment shown in FIG. 14, the optional platingoperation 1414 is performed after the optional flattening operation1412, which in turn is performed after the optional annealing operation1411. While such order is preferred, it will be appreciated that inother embodiments the order of the optional finishing steps 1411, 1412and 1414 may be rearranged. The primary considerations for the orderingof these finishing steps is whether later steps will damage the resultsof earlier steps. For example, it would be impractical to performplating step 1414 before the flattening step 1412 if the flattening wasto be carried out by grinding, while it might be acceptable if theflattening was to be carried out by pressing.

Referring now to FIGS. 15 a and 15 b, there is illustrated a method formanufacturing multiple cover assemblies simultaneously in accordancewith another embodiment of the current invention. Shown in FIG. 15 a isan exploded view of a multi-unit assembly, which can be subdivided afterfabrication to produce individual cover assemblies. The multi-unitassembly 1500 includes a frame 1502 and a sheet 1504 of a transparentmaterial. The frame 1502 has sidewalls 1506 defining a plurality offrame apertures 1508 therethrough. Each frame aperture 1508 iscircumscribed by a continuous sidewall section having a frame seal-ringarea 1510 (denoted by cross-hatching). Each frame seal-ring area 1510has a metallic surface, which may result from the inherent material ofthe frame 1502 or it may result from metal layers, which have beenapplied to the surface of the frame. In some embodiments, the frame 1502includes reduced cross-sectional thickness areas 1509 formed on theframe sidewalls 1506 between adjacent frame apertures 1508. FIG. 15 bshows the bottom side of the frame 1502, to better illustrate thereduced cross-sectional thickness areas 1509 formed between eachaperture 1508. Also illustrated is the base seal-ring area 1520 (denotedby cross-hatching) which surrounds each aperture 1508 to allow joiningto the package bases 104.

Further regarding the multi-aperture frames illustrated in FIGS. 15 aand 15 b, it will be understood that the frame 1502 can be attached asshown, with the open ends of the V-shaped notches facing away from thesheet, or alternatively, with the open ends of the V-shaped notchesfacing toward the sheet.

Except for the details just described, the multiple-aperture frame 1502of this embodiment shares material, fabrication and design details withthe single aperture frame 302 previously described. In this regard, apreferred embodiment of the frame 1502 is primarily formed of Kovaralloy or similar materials and more preferably, will have a Kovar alloycore with a surface layer of gold overlaying an intermediate layer ofnickel as previously described.

The transparent sheet 1504 for the multi-unit assembly can be formedfrom any type of transparent material as previously discussed for sheet304. In this embodiment, however, the sheet 1504 has a plurality ofwindow portions 1512 defined thereupon, with each window portion havingfinished top and bottom surface 1514 and 1516, respectively. A pluralityof sheet seal-ring areas 1518 are denoted by cross-hatching surroundingeach window portion in FIG. 15 a. With respect to the material of thesheet 1504, with respect to the finished configuration of the top andbottom surfaces 1514 and 1516, respectively, of each window portion1512, with respect to surface treatments, and/or coatings, the sheet1504 is substantially identical to the single window portion sheet 304previously discussed.

The next step of the process of manufacturing the multi-unit assembly1500 is to prepare the sheet seal-ring areas 1518 for metallization. Asnoted earlier, each sheet seal-ring area 1518 circumscribes a windowportion of the sheet 1504. The sheet seal-ring areas 1518 typically havea configuration which closely matches the configuration of the frameseal-ring areas 1510 to which they will eventually be joined. It will beappreciated, however, that in some cases other considerations willaffect the configuration of the frame grid, e.g., when electricalresistance heating is used to produce bonding, then the seal-ring areas1518 must be connected to form the appropriate circuits. The steps ofpreparing the sheet seal-ring areas 1518 for metallization issubstantially identical to the steps and options presented duringdiscussion of preparing the frame seal-ring area 310 on the singleaperture frame 302. Thus, at a minimum, preparing the sheet seal-ringarea 1518 typically involves a thorough (e.g., plasma, solvent ordetergent) cleaning to remove any contaminants from the surfaces andtypically also involves roughening the seal-ring area by chemicaletching, laser ablating, mechanical grinding or sandblasting this area.

The step of metallizing the prepared sheet seal-ring areas 1510 of thesheet 1502 are substantially identical to the steps described formetallizing the frame seal-ring area 310 on the single aperture frame302. For example, the metal layers shown in Examples 1 through 120 canbe used in connection with thermal compression bonding, for solderingwhere the solder material is plated onto the sheet as a final metalliclayer, and can be used in connection with soldering in combination witha separate gold-tin of solder preform and also for soldering inconnection with solders deposited or formed using inkjet technology.

The next step of the process is to position the frame 1502 against thesheet 1504 (it being understood that solder preforms or solder layerswould be interposed between the frame and the sheet if braze solderingis used to join the frame 1502 to the sheet 1504) such that each of thewindow portions 1512 overlays one of the frame apertures 1508, and thatfor each such window portion/frame aperture combination, at least aportion of the associated frame seal-ring area 1510 and at least aportion of the associated sheet seal-ring area 1518 contact one anotheralong a continuous junction region that circumscribes the associatedwindow portion. This operation is generally analogous to the steps ofpositioning the frame against the sheet in the single apertureembodiment previously described. If diffusion bonding is used to jointhe frame 1502 to the sheet 1504, an interlayer or innerlayer betweenthe frame 1502 to the sheet 1504 may or may not be employed.

Referring now to FIG. 16 a, there is illustrated the positioning of amulti-window sheet 1504 (in this case having window portions 1512 withcontoured surfaces) against a multi-aperture frame 1502 using complianttooling in accordance with another embodiment. The compliant toolingincludes a compliant element 1650 and upper and lower support plates1652, 1654, respectively. The support plates 1652 and 1654 receivecompressive force, denoted by arrows 1656, at discrete locations fromtooling fixtures (not shown). The compliant member 1650 is positionedbetween one of the support plates and the cover assembly pre-fab (i.e.,frame 1502 and sheet 1504). The compliant member 1650 yields elasticallywhen a force is applied, and therefore can conform to irregular surfaces(such as the sheet 1504) while at the same time applying a distributedforce against the irregular surface to insure that the required contactpressure is achieved all along the frame/sheet junction. Such complianttooling can also be used to press a sheet or frame against the othermember when the two members are not completely flat, taking advantage ofthe inherent flexibility (even if small) present in all materials. Inthe illustrated example, the compliant member 1650 is formed from asolid block of an elastomer material, e.g., rubber, however in otherembodiments the compliant member may also be fabricated from discreteelements, e.g., springs. The compliant material must be able towithstand the elevated temperatures experienced during the bondingoperation.

The next step of the process is heating all of the junction regionsuntil a metal-to-metal joint is formed between the frame 1502 and thesheet 1504 all along each junction region, thus creating the multi-unitassembly 1500 having a hermetic frame/sheet seal circumscribing eachwindow portion 1512. If diffusion bonding is used to join the frame 1502and the sheet 1504, the bond could be between the outermost metal layerof the frame and the non-metallized sheet 1504. It will be appreciatedthat any of the heating technologies previously described for joiningthe single aperture frame 302 to the single sheet 304 are applicable tojoining the multi-aperture frame 1502 to the corresponding multi-windowsheet 1504.

Referring now to FIG. 16 b, the final step of the current process is todivide the multi-unit assembly 1500 along each junction region that iscommon between two window portions 1512 taking care to preserve andmaintain the hermetic seal circumscribing each window portion. Aplurality of individual cover assemblies are thereby produced. FIG. 16b, illustrates a side view of a multi-unit assembly 1500 following thehermetic bonding of the sheet 1504 to the frame 1502. Where the frame1502 includes reduced cross-sectional thickness areas 1509, the step ofdividing the multi-unit assembly may include scoring the frame along theback side of the reduced cross-sectional thickness area at the positionindicated by arrow 1602, preferably breaking through or substantiallyweakening the remaining frame material below area 1509, and alsosimultaneously scoring the sheet 1504 along a line vertically adjacentto area 1509, i.e., at the point indicated by arrow 1604, followed byflexing the assembly 1500, e.g., in the direction indicated by arrows1606 such that a fracture will propagate away from the score along line1608, thereby separating the assembly into two pieces. This procedurecan be repeated along each area of reduced cross-sectional thickness1509 until the multi-unit assembly 1500 has been completely subdividedinto single aperture cover assemblies that are substantially identicalto those produced by the earlier method described herein. In otherembodiments, instead of using the score-and-break method, the coverassemblies may be cut apart, preferably from the frame side along thepath indicated by arrow 1602 (i.e., between the window portions 1512),using mechanical cutting, dicing wheel, laser, water jet or otherparting technology.

Referring now to FIGS. 17 a and 17 b, there is illustrated yet anothermethod for simultaneously manufacturing multiple cover assemblies. Thismethod expands upon the cold gas dynamic spray technique used to buildan integral frame/heat spreader directly upon the transparent sheetmaterial as previously illustrated in connection with FIGS. 12 a through12 c and FIGS. 13 a through 13 c. As shown in FIG. 17 a, the processstarts with a sheet of nonmetallic transparent material 1704 having aplurality of window portions 1712 defined thereupon, each window portionhaving finished top and bottom surfaces 1714 and 1716, respectively. Theproperties and characteristics of the transparent sheet 1704 areidentical to those in the embodiments previously discussed. The nextstep of the process involves preparing a plurality of frame attachmentareas 1720 (denoted by the path of the broken line surrounding eachwindow portion 1712), each frame attachment area 1720 circumscribing oneof the window portions 1712. As in previous embodiments, the step ofpreparing the frame attachment areas may comprise cleaning, roughening,grinding or otherwise modifying the frame attachment areas inpreparation for metallization.

The next step in this process is metallizing the prepared frameattachment areas on the sheet, i.e., this metallization may be performedusing a cold gas dynamic spray technology or where the layers arerelatively thin, using a CVD, physical vapor deposition or otherconventional metal deposition techniques. It will be appreciated thatthe primary purpose of this step is to apply metal layers necessary toobtain good adhesion to the transparent sheet 1704 and/or to meet themetallurgical requirements for corrosion prevention, etc.

Referring now to FIG. 17 b, the next step of the process is depositingmetal onto the prepared/metallized frame attachment areas of the sheet1704 using cold gas dynamic spray deposition techniques until a built-upmetal frame 1722 is formed upon the sheet having a seal-ring area 1726that is a predetermined vertical thickness above the frame attachmentareas, thus creating a multi-unit assembly having an inherent hermeticseal between the frame 1722 and the sheet 1704 circumscribing eachwindow portion 1712. In some embodiments, reduced cross-sectionalthickness areas 1724 are formed by selectively depositing the metalduring the cold spray deposition. In other embodiments, the reducedcross-sectional area sections 1724 may be formed following deposition ofthe frame/heat spreader 1722 through the use of grinding, cutting orother mechanical techniques such as laser ablation and water jet. Inaddition, the reduced cross-sectional area sections 1724 may be formedfollowing deposition of the frame/heat spreader 1722 through the use ofphoto-chemical machining (PCM).

The next step of the process which, while not required is stronglypreferred, is to flatten, if necessary, the seal-ring area 1726 of thesprayed-on frame 1722 to meet the flatness requirements for joining itto the package base 104. This flattening can be accomplished bymechanical means, e.g., grinding, lapping, polishing, etc., or by othertechniques such as laser ablation.

The next step of the process, which, while not required, is stronglypreferred, is to add additional metallic layers, e.g., a nickel layerand preferably also a gold layer, to the seal-ring area 1726 of thesprayed-on frame 1722 to facilitate welding the cover assembly to thepackage base 104. These metallic layers are preferably added using asolution bath plating process, e.g., solution bath plating, althoughother techniques may be used.

The next step of the process is dividing the multi-unit assembly 1700along each frame wall section common between two window portions 1712while, at the same time, preserving and maintaining the hermetic sealcircumscribing each window portion. After dividing the multi-unit 1700,a plurality of single aperture cover assemblies 1728 (shown in brokenline) will be produced, each one being substantially identical to thesingle aperture cover assemblies produced using the method described inFIGS. 12 a through 12 c and FIGS. 13 a through 13 c. All of the options,characteristics and techniques described for use in the single unitcover assembly produced using cold gas dynamic spray technology areapplicable to this embodiment. It will be appreciated that certainoperations for example, the flattening of the frame and the plating ofthe frame with additional metallic layers, may be performed on themulti-unit assembly 1700, prior to separation of the individual units,or on the individual units after separation.

As previously described, heating the junction region between themetallized seal-ring area of the transparent sheet and the seal-ringarea of the frame is required for forming the hermetic sealtherebetween. Also as previously described, this heating may beaccomplished using a furnace, oven, or various electrical heatingtechniques, including electrical resistance heating (ERH). Referring nowto FIGS. 18 a-18 c, there is illustrated methods of utilizing electricresistance heating to manufacture multiple cover assembliessimultaneously.

Referring first to FIG. 18 a, there is illustrated a transparent sheet1804 having a plurality of seal-ring areas 1818 laid out in arectangular arrangement around a plurality of window portions 1812.These seal-ring areas 1818 have been first prepared, and then metallizedwith one or more metal or metal alloy layers, as previously describedherein. The transparent sheet 1804 further includes an electrode portion1830, which has been metallized, but does not circumscribe any windowportions 1812. This electrode portion is electrically connected to themetallized seal-ring areas 1818 of the sheet. One or more electrode pads1832 may be provided on the electrode portion 1830 to receive electricalenergy from electrodes during the subsequent ERH procedure.

Referring now to FIG. 18 b, there is illustrated a frame 1802 having aplurality of sidewalls 1806 laid out in a rectangular arrangement arounda plurality of frame apertures 1808. The apertures 1808 are disposed soas to correspond with the positions of the window portions 1812 of thesheet 1804, and the sidewalls 1806 are disposed so that frame seal-ringareas 1810 (located thereupon) correspond with the positions of thesheet seal-ring areas 1818 of the sheet. The frame is metallic ormetallized in order to facilitate joining as previously describedherein. The frame 1802 further includes an electrode portion 1834 thatdoes not circumscribe any frame apertures 1808. This frame electrodeportion 1834 is positioned so as not to correspond to the position ofthe sheet electrode portion 1830, and preferably is disposed on anopposing side of the sheet-window/frame-grid assembly (i.e., when thesheet is assembled against the frame). The frame electrode portion 1834is electrically connected to the metallized frame seal-ring areas 1810.One or more electrode pads 1836 may be provided on the electrode portion1834 to receive electrical energy from electrodes during the subsequentERH procedure.

Referring now to FIG. 18 c, the sheet 1804 is shown positioned againstthe frame 1802 in preparation for heating to produce the hermetic sealtherebetween. If applicable, solder or a solder preform has beenpositioned therebetween as previously described. It will be appreciatedthat when the transparent sheet 1804 is brought against the frame 1802,the metallized seal-ring areas 1818 on the lower surface of the sheetwill be in electrical contact with the metallized seal-ring areas 1810on the upper surface of the frame. However, the sheet electrode portion1830 and the frame electrode portion 1834 will not be in direct contactwith one another, but instead will be electrically connected onlythrough the metallized seal-ring areas 1818 and 1810 to which they are,respectively, electrically connected. When an electrical potential isapplied from electrode pads 1832 to electrode pads 1836 (denoted by the“+” and “−” symbols adjacent to the electrodes), electrical currentflows through the junction region of the entire sheet-window/frame-gridassembly. This current flow produces electrical resistance heating (ERH)due to the resistance inherent in the metallic layers. In someembodiments, this electrical resistance heating may be sufficient tosupply the necessary heat, in and of itself, to result in TC bonding,soldering, or other hermetic seal formation between the sheet 1804 andthe frame 1802 in order to form a multi-unit assembly. In otherembodiments, however, electrical resistance heating may be combined withother heating forms such as furnace or oven pre-heating in order tosupply the necessary heat required for bonding to form the multi-unitassembly.

After bonding the sheet 1804 to the frame 1802 to form the multi-unitassembly, the sheet electrode portion 1830 and the frame electrodeportion 1834 can be cut away and discarded, having served their functionof providing electrical access for external electrodes (or otherelectrical supply members) to the metallized seal-ring areas of thesheet and frame, respectively. The removal of these “sacrificial”electrode portions 1830 and 1834 may occur before or during the “dicing”process step, i.e., the separating of the multi-unit assembly intoindividual cover assemblies. It will be appreciated that any of thetechnologies previously described herein for separating a multi-unitassembly into individual cover assemblies can be used for the dicingstep of separating a multi-unit assembly fabricated using ERH heating.

Where ERH is to be used for manufacturing multiple cover assembliessimultaneously, the configuration of the sheet-window/frame-grid arrayand/or the placement of the electrodes portions within thesheet-window/frame-grid array may be selected to modify the flow ofcurrent through the junction region during heating. The primary type ofmodification is to even the flow of current through the various portionsof the sheet-window/frame-grid during heating to produce more eventemperatures, i.e., to avoid “hot spots” or “cold spots.”

Referring now to FIGS. 19 a-19 f, there are illustrated varioussheet-window/frame-grid configurations adapted for producing more eventemperatures during ERH. In each of FIGS. 19 a-19 f, there is shown asheet-window/frame-grid array 1900 comprising a prepared, metallizedtransparent sheet 1904 overlying a prepared, metallic/metallized frame1902. The window portions of the sheet 1904 directly overlie the frameapertures of the frame 1902, and the metallized seal-ring areas of thesheet directly overlie the seal-ring areas of the frame (it will beappreciated that metallized portions of the sheet 1904 and the frame1902 appear coincident in these figures). Metallized electrode portionsformed on the transparent sheet 1904 are denoted by reference letters A,B, C and D. These electrode portions A, B, C and D are electricallyconnected to the adjoining sheet seal-ring areas of the sheet, but areelectrically insulated from one another by non-metallized areas 1906 ofthe sheet. An external electrode is applied to the top of themetallic/metallized frame (on the side opposite from the sheet) acrossthe area denoted by reference letter E. For bonding or soldering,electrical power is applied at the electrodes, e.g., one line toelectrodes A, B, C and D simultaneously, and the other line to electrodeE, or alternatively, one line in sequence to each of electrode A, B, Cand D, and the other line to electrode E. It will be appreciated thatmany other combinations of electrode powering are within the scope ofthe invention.

Referring to FIG. 19 f, this embodiment illustrates asheet-window/frame-grid 1900 having a “shingle” configuration, i.e.,where the seal-ring areas between the window portions/frame apertures donot form continuous straight lines across the assembly array.Shingle-arrangement frame assemblies are more labor-intensive toseparate using scribe-and-break or cutting procedures. Separating suchassemblies requires that each row first be separated from the overallgrid, and then that individual cover assemblies be separated from therow by separate scribe-and-break or cutting operations. Nevertheless,use of shingle-arrangement assemblies may have benefits relating toheating using ERH techniques.

It will be understood that a metal frame such as 1802 or 1902, which maycontain one or more added layers on its exterior, including but notlimited to metal or metal alloy layers, may be diffusion bonded to anon-metallized sheet using ERH techniques to apply heat to the frame.The amount of temperature rise throughout the thickness of thenon-metallized sheet will depend on the intensity and duration of theapplication of the electrical power (voltage and amperage) to the frame,as well as other factors. An innerlayer or interlayer material may beemployed between the frame and the sheet during the diffusion bondingprocess, as discussed previously.

It will further be appreciated that the terms “thermal compressionbonding” (and its abbreviation “TC bonding”) and “diffusion bonding” areused interchangeably throughout this application. The term “diffusionbonding” is preferred by metallurgists while the term “thermalcompression bonding” is preferred in many industries (e.g.,semiconductor manufacturing) to avoid possible confusion with othertypes of “diffusion” processes used for creating semiconductor devices.Regardless of which term is used, as previously discussed, diffusionbonding refers to the family of bonding methods using heat, pressure,specific positive or negative pressure atmospheres and time alone tocreate a bond between mating surfaces at a temperature below the normalfusing temperature of either mating surface. In other words, neithermating surface is intentionally melted, and no melted filler material isadded, nor any chemical adhesives used.

As previously described, diffusion bonding utilizes a combination ofelevated heat and pressure to hermetically bond two surfaces togetherwithout first causing one or both of the adjoining surfaces to melt (asis the case with conventional soldering, brazing and welding processes).When making optical cover assemblies, wafer level assemblies or othertemperature-sensitive articles, it is almost always required that thebonding temperatures remain below some upper limit. For example, inoptical cover assemblies, the bonding temperature should be below theT_(G) and the softening temperature, T_(S), of the sheet material so asnot to affect the pre-existing optical characteristics of the sheet. Asanother example, in wafer level assemblies, the bonding temperatureshould be below the upper temperature limit for the embedded microdevice and/or its operating atmosphere (i.e., the gas environment insidethe sealed package). However, the specific temperature and pressureparameters required to produce a hermetic diffusion bond can vary widelydepending upon the nature and composition of the two mating surfacesbeing joined. Therefore, it is possible that some combinations oftransparent sheet material (e.g., glass) and frame material (e.g.,metals or metallized non-metals), or some combinations of framematerials and substrate materials (e.g., silicon, alumina or metals),will have a diffusion bonding temperature that exceeds the T_(G) and/orthe T_(S) of the sheet material, or that exceeds some other temperaturelimit. In such cases, it might appear that diffusion bonding isunsuitable for use in hermetically joining the components together ifthe temperature limits are to be followed. In fact, however, it has beendiscovered that the use of “interlayers,” i.e., intermediate layers ofspecially selected material, placed between the sheet material and theframe, or between the frame material and the substrate material, cancause hermetic diffusion bonding to take place at a substantially lowertemperature than if the same sheet material was bonded directly to thesame frame material, or if the same frame material was bonded directlyto the same substrate material. Note that the terms “interlayers” and“innerlayers” are used interchangeably throughout this application, asboth terms may be encountered in the art for the same thing.

A properly matched interlayer improves the strength and hermeticity(i.e., gas tightness or vacuum tightness) of a diffusion bond. Further,it may promote the formation of compatible joints, produce a monolithicbond at lower bonding temperatures, reduce internal stresses within thebond zone, and prevent the formation of extremely stable oxides whichinterfere with diffusion, especially on the surface of Al, Ti andprecipitation-hardened alloys. The interlayer is believed to diffuseinto the parent material, thereby raising the melting point of the jointas a whole. Depending upon the materials to be joined by diffusionbonding, the interlayer material could be composed of a metal, a metalalloy, a glass material, a solder glass material including solder glassin tape or sheet form, or other materials. In the diffusion bonding ofBT5-1 Ti alloy to Armco iron, an interlayer of molybdenum foil 0.3 mmthick has been used. Reliable glass-to-glass and glass-to-metal bondsare achieved with metal interlayers such as Al, Cu, Kovar, Niobium andTi in the form of foil, usually not over 0.2 mm thick. The interlayersare typically formed into thin preforms shaped like the seal ring areaof the mating surfaces to be joined.

It is important to distinguish the use of diffusion bonding interlayersfrom the use of conventional solder preforms and other processespreviously disclosed. For purposes of this application, an interlayer isa material used between sealing surfaces to promote the diffusionbonding of the surfaces by allowing the respective mating surfaces todiffusion bond to the interlayer rather than directly to one another.For example, with the proper interlayer material, the diffusion bondingtemperature for the joint between the sheet material and interlayermaterial, and for the joint between the interlayer material and theframe material, may be substantially below the diffusion bondingtemperature of a joint formed directly between the sheet material andthe frame material. Thus, use of the interlayer allows diffusion bondingof the sheet to the frame at a temperature which is substantially belowthe diffusion bonding temperature that would be necessary for bondingthat sheet material and that frame material directly. The hermetic jointis still formed by the diffusion bonding process, i.e., none of thematerials involved (the sheet material, the interlayer material nor theframe material) melts during the bonding process. This distinguishesdiffusion bonding using interlayers from other processes such as the useof solder preforms in which the solder material actually melts to formthe bond between the materials being joined. It is possible to usematerials conventionally used for solders, for example, Au—Sn solderpreforms, as interlayers for diffusion bonding. However, when used asinterlayers they are used for their diffusion bonding properties and notas conventional solders (in which they melt).

The use of interlayers in the production of window assemblies or otherpackaging may provide additional advantages over and above their use aspromoting diffusion bonding. These advantages include interlayers whichserve as activators for the mating surfaces. Sometimes the interlayermaterials will have a higher ductility in comparison to the basematerials. The interlayers may also compensate for stresses which arisewhen the seal involves materials having different coefficients ofthermal expansion or other thermal expansion properties. The interlayersmay also accelerate the mass transfer or chemical reaction between thelayers. Finally, the interlayers may serve as buffers to prevent theformation of undesirable chemical or metallic phases in the jointbetween components.

Referring now to FIGS. 20 a and 20 b, there is illustrated a windowcover assembly including interlayers to promote joining by diffusionbonding. In this embodiment, the window assembly 2050 includes atransparent glass sheet 2052, an interlayer 2054 and a metal or metalalloy base 2056. The base 2056 includes a built-up seal ring area 2058and a flange 2060 which facilitates the subsequent electric resistanceseam welding of the finished window assembly to a package base or otherhigher level portion of the final component. The interlayer 2054 in thisembodiment takes the form of a metallic preform which has theconfiguration selected to match the seal ring area 2058 of the frame. Toform the hermetic window assembly, the sheet 2052, interlayer 2054 andframe 2056 are placed in a fixture (i.e., tooling) or mechanicalapparatus (not shown) which can provide the required predeterminedbonding pressure between the seal ring areas of the respectivecomponents. In some cases, the fixture may serve only to align thecomponents during bonding, while the elevated bonding pressure isapplied from a mechanical apparatus such as a ram. In other cases,however, the fixture may be designed to constrain the expansion of thestacked components during heating (i.e., along the stacking axis),whereby the thermal expansion of the assembly components toward thefixture, and of the fixture itself toward the components, will“self-generate” some or all of the necessary bonding pressures betweenthe components as the temperature increases.

Referring now to FIGS. 20 e and 20 f, an example of a “self-compressing”fixture assembly is shown. As best seen in FIG. 20 e, the fixture 2085includes an upper fixture member 2086 and a lower fixture member 2087,which together define a cavity 2088 for receiving the window assemblycomponents to be bonded. Clamps 2089 are provided which constrain theoutward movement of the fixture members 2086 and 2087 in the axialdirection (denoted by arrow 2090). Generally, the CTE of the materialforming the clamps 2089 will be lower than the CTE of the materialforming the fixture members 2086 and 2087. FIG. 20 f shows thecomponents for the window assembly 2070 (FIGS. 20 c and 20 d) loadedinto the cavity 2088 of the fixture 2085 in preparation for bonding.Note that while the fixture members 2086 and 2087 are in contact withthe upper and lower surfaces of the window components, a small gap 2097is left between the fixture members themselves to allow the members toexpand axially toward one another when heated (since they areconstrained by the clamps). Also, note that a small gap 2098 isgenerally left between the lateral sides of the window assemblycomponents and the fixture members 2086 and 2087 to minimize the lateralforce exerted on the components by the fixture members during heating.When the fixture 2085 is heated, the inner surfaces (i.e., facing thecavity 2088) of the fixture members 2086 and 2087 will expand (due tothermal expansion) axially toward one another against the windowcomponents, and the window components will expand outward against thefixture. These thermal expansions can press the window componentsagainst one another with great force in the axial direction tofacilitate diffusion bonding. It will be appreciated that thermalexpansion of the fixture members 2086 and 2087 will also occur in thelateral direction (denoted by arrow 2091). While this lateral expansionis not generally desired, in most cases is will not present an obstacleto the use of self-compressing fixtures.

Referring now to FIG. 20 g, there is illustrated an alternativeself-compressing fixture adapted to enhance thermal expansion (and hencecompression) in the axial direction 2090 without causing excessivethermal expansion in the lateral direction 2091. As with the previousexample, alternative fixture 2092 includes an upper fixture member 2086and a lower fixture member 2087 defining a cavity 2088 for receiving thewindow assembly components to be bonded, and clamps 2089 (only one ofwhich is shown for purposes of illustration) which constrain the outwardmovement of the fixture members in the axial direction 2090. Also as inthe previous embodiment, a first small gap 2097 is present between thefixture members 2086 and 2087 themselves, and a second small gap 2098 ispresent between the lateral sides of the window components and thefixture members. Unlike the previous embodiment, however, each fixturemember 2086 and 2087 of the alternative fixture 2092 comprises twosub-members, namely, first sub-members 2093 and 2094, respectively,adapted to bear primarily axially against the window assembly components(not shown), and second sub-members 2095 and 2096, respectively, adaptedto hold and align the window assembly components in the cavity. Byselecting a material for the first sub-members 2093 and 2094 having ahigh CTE, axial expansion (and hence compression) during heating will becorrespondingly high. However, lateral expansion and relative lateralmovement between the second sub-members 2095 and 2096 and the windowcomponents can be minimized by selecting a different material for thesecond sub-members, namely, a material having a lower CTE (i.e., lowerthan the CTE for the first sub-members). Preferably, the CTE of thesecond sub-members 2095 and 2096 will be close to the CTE for theadjacent window components.

Referring again to FIGS. 20 a and 20 b, the assembled (but not yetbonded) components of the window assembly 2050 are then heated until thediffusion bonding pressure/temperature conditions are reached, and theseconditions are maintained until a first diffusion bond is formed betweenthe sheet 2052 and the interlayer 2054, and a second diffusion bond isformed between the interlayer 2054 and the seal ring area 2058 of theframe 2056. It will be understood that the first bond between the sheetand the interlayer may actually occur before, after or simultaneouslywith, the second bond between the interlayer and the frame. Aspreviously explained, it will also be understood that the order ofapplying heat and pressure to form the diffusion bond is not believed tobe significant, i.e., in other words whether the pre-determined pressureis applied, and then the heat is applied or whether the heat is appliedand then the predetermined pressure is applied, or whether both heat andpressure are increased simultaneously is not believed to be significant,rather the diffusion bonding will occur when the preselected pressureand temperature are present in the bond region for a sufficient amountof time. After the diffusion bonds are formed, the sheet 2052 will behermetically bonded to the frame 2056 to form a completed windowassembly 2050 as shown in FIG. 20 b.

In further embodiments of the current invention, it has been discoveredthat clean, i.e., unmetallized, glass windows may be directly bonded toframes of Kovar or other metallic materials using diffusion bonding.This is in addition to the diffusion bonding of metallized glass windowsto Kovar frames as previously described. Optionally, the directdiffusion bonding of unmetallized glass windows to metallic frames maybe enhanced through the use of certain compounds, e.g.,molybdenum-manganese, on the frames. Whether the glass is metallized orunmetallized, the diffusion bonding is most commonly performed in avacuum; however, it may be performed in various other atmospheres. Theuse of oxidizing atmospheres is typically not required, however, as anyresulting oxides tend to be dispersed by pressures encountered in thebonding operation. In still other embodiments, of the invention,diffusion bonding can be used for joining frames made of Kovar and othermetallic materials directly to sheets or wafers of semiconductormaterials including silicon and gallium arsenide (GaAs).

Since successful diffusion bonding requires the mating surfaces beingbonded to be brought into intimate contact with one another, the surfacefinish characteristics of the mating surfaces may be importantparameters of the invention. It is believed that the following matingsurface parameters will allow successful diffusion bonding between themating surfaces of Kovar frames and thin sheet materials including, butnot limited to, Kovar to metallized glass, Kovar to clean (i.e.,unmetallized) glass, Kovar to metallized silicon, Kovar to clean (i.e.,unmetallized) silicon, Kovar to metallized gallium arsenide (GaAs) andKovar to clean (i.e., unmetallized) GaAs: Parallelism of sheet material(i.e., uniformity of thickness) within the range of ±about 12.7°microns; Surface flatness (i.e., deviation in height per unit lengthwhen placed on ideal flat surface) within range from 5 mils/inch toabout 10 mils/inch; Surface roughness not more than about 16micro-inches (0.4064 microns). These surface parameters can also be usedfor diffusion bonding of Kovar directly to Kovar, e.g., to manufacturebuilt-up metallic frames.

The temperature parameters for diffusion bonding between the matingsurfaces of Kovar frames and the thin sheet materials described aboveare believed to be within the range from about 40% to about 70% of theabsolute melting temperature, in degrees Kelvin, of the parent materialhaving the lower melting temperature. When diffusion bonding is used forbonding optically finished glass or other transparent materials, thebonding temperature may be selected to be below the T_(G) and/or thesoftening temperature of the for the glass other transparent materials,thereby avoiding damage to the optical finish. Depending upon thebonding temperature selected, in some embodiments the application ofoptical and/or protective coatings to the transparent sheets (i.e., thatbecome the windows) may be performed after the bonding of the sheets tothe frames, rather than before bonding. In other embodiments, some ofthe optical and/or protective coatings may be applied to the glasssheets prior to bonding, while other coatings may be applied subsequentto bonding. With regard to pressure parameters, a pressure of 105.5kg/cm² (500 psi) is believed suitable for diffusion bonding Kovar framesand the thin sheet materials previously described.

It will be noted that since the diffusion bonding occurs at hightemperature, the CTE of the glass sheet should be matched to the CTE ofthe metallic frame. To the extent that the CTEs cannot be completelymatched (e.g., due to non-linearities in the CTEs over the range ofexpected temperatures), then it is preferred that the CTE of the glasssheet be lower than the CTE of the metallic frame. This will result inthe metallic frame shrinking more than the glass sheet as the combinedwindow/frame assembly cools from its elevated bonding temperature (orfrom an elevated operational temperature) back to room temperature. Theglass will therefore be subjected primarily to compression stress ratherthan tension, which reduces the tendency for cracking.

Referring now to FIGS. 20 c and 20 d, there is illustrated an additionalembodiment of the invention, a window assembly having internal andexternal frames. FIG. 20 c illustrates the components of window assembly2070 before assembly, while FIG. 20 d illustrates the completedassembly. The window assembly 2070 includes separate frame members 2072and 2074, which are bonded (using diffusion bonding, soldering, brazingor other techniques disclosed herein) to the inner and outer surfaces2076 and 2078, respectively, of the transparent sheet 2080. In otherwords, the transparent window material is “sandwiched” between a layerof frame material on the top of the window and a layer of frame materialon the bottom of the window. Interlayers 2082 and 2084 may be providedfor diffusion bonding as previously described, or alternatively, solderpreforms (also shown as 2082 and 2084) may be provided for bonding bysoldering as previously described.

Typically, the same bonding technique will be used for bonding both theinternal and external frames to the window, however, this is notrequired. Similarly, the internal and external bonds will typically beformed at the same time, however, this in not required. The internalframe 2072 must, however, be hermetically bonded to the window 2080 toproduce a hermetic window assembly. A hermetic bond is not typicallyrequired for bonding the external frame 2074 to the window 2080,however, it may be preferred for a number of reasons.

One benefit of window assemblies having the so-called “sandwiched” frameconfiguration is to equalize the stresses on the internal and externalsurfaces, 2076 and 2078, respectively, of the transparent sheet 2080that are caused by differential thermal expansion characteristics of theframes 2072 and 2074 and sheet (due to unequal CTE), e.g., duringcooling after bonding, or during thermal cycling. Put another way, whena window assembly has a frame bonded to only one surface, unevenexpansion and contraction between the frame and sheet may producesignificant shear stresses within the sheet. These shear stresses may bestrong enough to cause shear failure (e.g., cracking or flaking) withinthe transparent sheet even though the window-to-frame bond itselfremains intact. When a frame is bonded to both the internal and externalsurfaces of the window, however, the shear stresses within the glass (orother transparent material) may be significantly reduced. This isparticularly true if the same material or material having similar CTEsare used for both the internal and external frames. Thisstress-equalization through the thickness of the window increases thereliability and durability of the assembled window during subsequentthermal cycling and/or physical shock.

Sandwiched construction may be used in window assemblies or in WLPassemblies. Sandwiched construction with internal and external frames isespecially advantageous where the sheet and frame materials havesignificantly different CTEs. In addition to the stress balancingfeatures of sandwiched construction, use of an external frame on thesheet may have additional benefits, including: enhancing thermalspreading across the window; enhancing heat dissipation from theassembly; serving as an optical aperture; facilitating thealigning/fixturing or clamping of the device during bonding or assemblyto higher level assemblies; and to display working symbolization.

Referring now to FIGS. 21 a and 21 b, there are illustrated two examplesof hermetically sealed wafer-level packages (also known as “WLPs”) formicro-devices in accordance with other embodiments of the invention.These embodiments are substantially similar to one another, except thatwafer-level package 2002 (FIG. 21 a) has reverse-side externalelectrical connections while wafer-level package 2024 (FIG. 21 b) hassame-side external electrical connections. The wafer-level packages,while similar in many respects to the discrete device packagespreviously disclosed herein, utilize the substrate of the micro-deviceitself, typically a semiconductor substrate, as a portion of thepackage's hermetic envelope. Such wafer-level packaging provides a veryeconomical method for hermetically encapsulating wafer-fabricatedmicro-devices, especially where high production volumes are involved. Aswill be described below, a single micro-device may be packaged using WLPtechnology, or multiple micro-devices on the original production wafermay be packaged simultaneously using WLP technology in accordance withvarious aspects of the current invention.

Referring now specifically to FIG. 21 a, the wafer-level package 2002encloses one or more micro-devices 2004, e.g., a MEMS device or MOEMSdevice fabricated on a substrate 2006. The substrate 2006 is typically awafer of silicon (Si) or gallium arsenide (GaAs) upon which electroniccircuitry 2008 associated with the micro-device 2004 is formed usingknown semiconductor fabrication methods. Electrical vias 2010 (shown inbroken line) may be formed in the substrate 2006 using known methods toconnect the circuitry 2008 to externally accessible connection pads 2012disposed on the reverse side (i.e., with respect to the device) of thesubstrate. It will be appreciated that the path of vias 2010 shown inFIG. 20 has been simplified for purposes of illustration. One end of aframe 2014 made of Kovar or other metallic material is hermeticallybonded to the substrate 2006, and a transparent window 2016 is, in turn,hermetically bonded to the other end of the frame to complete thehermetic envelope sealing the micro-device within the cavity 2018. Theframe-mating surfaces of the substrate 2006 may be prepared ormetallized with one or more metal layers 2020 to facilitate bonding tothe frame, and similarly the frame-mating surfaces of the window 2016may be prepared or metallized with one or more metal layers 2022 for thesame purpose.

Referring now specifically to FIG. 21 b, the wafer-level package 2024 issubstantially identical to the package 2002 previously described, exceptthat in this case the vias 2026 are routed to external connection pads2028 disposed on the same side of the substrate 2006. Obviously, in suchembodiments, the frame 2014 and window 2016 are dimensioned to leaveuncovered a portion of the substrate's upper surface.

Referring now to FIG. 21 c, there is shown an exploded view of a WLP2100 illustrating one possible method of manufacture. To packageindividual or multiple micro-devices using WLP methods, the followingcomponents are necessary: a substrate 2006 having a micro-device 2004thereupon; a frame/spacer 2014 having a continuous sidewall 2015 andthat is “taller” than the device to be encapsulated (to provideclearance); and a transparent sheet or window 2016. Depending upon thebonding method to be used, solder preforms of a metal alloy or glasscomposition, or interlayers for diffusion bonding 2102 and 2103 may alsobe required. It will be appreciated that the top preform 2102 (betweenthe window 2106 and the frame 2014) may be a different material than thebottom preform 2103 (between the frame 2014 and the substrate 2006).

Briefly, the steps for forming the package 2100 are as follows: A firstframe-attachment area 2104 is prepared on the surface of the wafersubstrate 2006 of the subject micro-device. This first frame-attachmentarea 2104 has a plan (i.e., configuration when viewed from above) thatcircumscribes the micro-device or micro-devices 2004 on the substrate2006. A second frame-attachment area 2106 is prepared on the surface ofthe window 2016. The second frame-attachment area 2106 typically has aplan substantially corresponding to the plan of the firstframe-attachment area 2104. The execution order of the previous twosteps is immaterial. Next, the frame/spacer 2014 is positioned betweenthe substrate 2006 and the window 2016. The frame/spacer 2014 has a plansubstantially corresponding to, and in register with, the plans of thefirst and second frame-attachment areas 2104 and 2106, respectively. Ifapplicable, the solder preforms 2102 and 2103 or diffusion bondinginterlayers 2102 and 2103 are interposed at this time between theframe/spacer 2014 and the frame-attachment areas 2104 and/or 2106.Finally, the substrate 2006, frame/spacer 2014 and window 2016 arebonded together (facilitated by solder or glass preforms 2102 and 2103or diffusion bonding interlayers 2102 and 2103, if applicable) to form ahermetically sealed package encapsulating micro-device 2004 within, butallowing light to travel to and/or from the micro-device through thetransparent aperture area 2108 of the window.

It will be understood that diffusion bonding of the package 2100 can beperformed in a single (combined) step or in a number of sub-steps. Forexample, all five components (sheet 2016, first interlayer 2102, frame2014, second interlayer 2103 and substrate 2006) could be stacked in asingle fixture and simultaneously heated and pressed together to causediffusion bonds to form at each of the sealing surfaces. Alternatively,the window sheet 2016 may be first diffusion bonded to the frame 2014using first interlayer 2102 (making a first subassembly), and then thisfirst subassembly may be subsequently diffusion bonded to the substrate2006 using second interlayer 2103. In another alternative, the frame2014 could be diffusion bonded to the substrate 2006 using secondinterlayer 2103, and then the transparent sheet 2016 may subsequently bebonded to the sub-assembly using first interlayer 2102. The choice ofwhich bonding sequence to be used would, of course, depend upon theexact materials to be used, the heat sensitivity of the transparentmaterial in the sheet 2016, the heat sensitivity of the micro device2004 and, perhaps, other parameters such as the expansioncharacteristics of the frame 2014 and interlayer materials.

It will further be appreciated that the current invention is similar inseveral respects to the manufacturing of the “stand-alone” hermeticwindow assemblies previously described. The preparing of theframe-attachment areas 2106 of the window 2016 may be performed usingthe same techniques previously described for use in preparing the sheetseal-ring area 318, including cleaning, roughening, and/or metallizingwith one or more metallic layers as set forth in the earlier Examples1-96.

While the transparent windowpane 2016 may be roughened (e.g., inpreparing the frame-attachment area 2106) to promote adhesion of thefirst metallic layer being deposited onto it (e.g., by CVD or PVD), thewafer substrate 2006 will not typically be roughened in the same manner.Instead, the initial metallic layer on the wafer substrate 2006 willtypically be deposited using conventional wafer fabrication techniques.Where conventional methods of wafer fabrication include the requirementor option of etching a silicon or GaAs wafer to promote adhesion of ametal's deposition, then the same practice may be followed in preparingthe frame attachment area 2104 on the wafer substrate 2006 when buildingWLP devices.

Other wafer or substrate materials include, but are not limited to,glass, diamond and ceramic materials. Some ceramic wafers are known asalumina wafers. These alumina wafers or substrates may be multi-layersubstrates, and may be manufactured using Low-Temperature Co-Fired(LTCC) or High-Temperature Co-Fired (HTCC) materials and processes. LTCCand HTCC substrates often have internal and external electricalcircuitry or interconnections. This circuitry is typically screenprinted onto the ceramic or alumina material layer(s) prior to co-firingthe layers together.

Also, any of the bonding techniques and parameters previously describedfor use on window assemblies may be used to hermetically bond the WLPcomponents to one another, including diffusion bonding/TC bonding withor without the use of interlayers, soldering using a solder preform andsoldering using inkjet-dispensed solders. The primary difference is thatwhen making “stand-alone” window assemblies, only two primary components(namely, the transparent sheet/window 304 and frame 302) are bondedtogether, while when making WLPs, three primary components (namely, thewindow 2016, frame 2014 and substrate 2006) are bonded together(sometimes simultaneously). Of course, when producing WLPs usingsoldering techniques, additional components may be required, for exampleone or more solder preforms 2102 or a quantity of inkjet-dispensedsolder. The solder preforms, if used, may be attached to the top and/orbottom of the frame 2014 as one step in the manufacture of that item.This will simplify the alignment of the three major components of theWLP assembly. It will, of course, be appreciated that thispre-attachment of the solder preforms to the frame is also applicable tothe “stand-alone” window assemblies previously described. One of themethods for attaching solder preforms to the window 2016, frame 2014and/or substrate 2006 is to tack the preform in place using a localizedheat source.

Prior to soldering components together, cleaning the surfaces of thesolder preforms and/or the metallized surfaces of the window 2016, frame2014 and/or substrate 2006 may be necessary to remove surface oxides. Itis desirable to avoid using fluxes during the soldering process toeliminate the need for post-soldering or defluxing. Several surfacepreparation technologies are available to prepare the metal and soldersurfaces for fluxless soldering.

Several other processes may be used for preparing the surfaces of windowassemblies or WLP components for soldering to avoid the need to removefluxes after soldering. A first option is to use what is known in thetrade as a no-clean flux. This type of flux is intended to be left inplace after soldering. A second option is the use of gas plasmatreatments for improving solderability without flux. For example, anon-toxic fluorine-containing gas may be introduced that reacts at thesurface of the solder. This reaction forms a crust on the solder anddissolves upon remelt. The welds and joints formed are equal to orbetter than those formed when using flux. Such plasmas offer benefitsincluding the removal by reduction of oxides and glass to promoteimprovements in solderability and wire bondability. Such treatments havebeen indicated on thick film copper, gold and palladium. Additionalcandidate gases for leaving a clean oxide-free surface include hydrogenand carbon monoxide plasma. Still further candidate gases includehydrogen, argon and freon gas combinations. One version of plasmatreatment is known as Plasma-Assisted Dry Soldering (PADS). The PADSprocess coverts tin oxide (present in fluxless solders when unstablereduced tin oxide reoxidizes upon exposure to air) to oxyfluorides thatpromote wetting. The conversion film breaks up when the solder melts andallows reflow. The film is understood to be stable for more than a weekin air and for more than two weeks when the parts are stored innitrogen.

As in the previously described methods for manufacture of individual andmultiple window assemblies for hermetically packaging discretemicro-devices, the selection of compatible materials for the variouscomponents for the manufacture of WLPs is another aspect of theinvention. For example, each of the primary components (e.g., window,frame/spacer and wafer substrate) of the WLP will preferably haveclosely matched CTEs to insure maximum long-term reliability of thehermetic seal. The frame/spacer 2014 may be formed of either a metallicmaterial or of a non-metallic material. The best CTE match will beachieved by forming the frame/spacer 2014 from the same material aseither the wafer substrate 2006 or the window 2016. However, galliumarsenide (GaAs) and silicon (Si) (i.e., the materials typically used forthe wafer substrate) and most glasses (i.e., the material that istypically used for the window) are relatively brittle, at least incomparison to most metals and metal alloys. These non-metallic materialsare therefore typically not as preferred for forming the frame/spacer2014 as are metals or metal alloys, because the metals and metal alloystypically exhibit better resistance to cracking. In fact, the use of ametal or metal alloy for the frame/spacer 2014 is believed to provideadditional resistance to accidental cracking or breaking of the wafersubstrate 2006, window 2016 and complete WLP 2002 after bonding. When ametallic frame/spacer 2014 is employed, it will preferably be platedwith either gold alone, or with nickel and then gold, sometimes tofacilitate diffusion bonding or soldering, but more often, to provide asurface on the frame/spacer that provides various kinds of protectionbetween the frame/spacer and the atmosphere inside the package. If,however, a non-metallic frame/spacer 2014 is employed, then it might bemetallized to facilitate diffusion bonding or soldering. The metallayers used on the frame/spacer 2014 may be the same as those used onthe windowpane 304 for the manufacture of window assemblies, e.g., thefinal layer might be one of chromium, nickel, tin, tin-bismuth and gold.

In selecting compatible materials for the components of WLPs, it isrecognized that silicon (Si) has a CTE ranging from about 2.6 PPM/° K at293° K to about 4.1 PPM/° K at 1400° K. If it is assumed that theoperating temperatures for micro-devices such as MEMS and MOEMS will bewithin the range from about −55° C. to about +125° C., and that theexpected diffusion bonding or soldering temperatures will be within therange from about +250° C. to about +500° C., it may be interpolated thatsilicon wafers of the type used for WLP substrates will have a CTEwithin the range from about 2.3 PPM/° K to about 2.7 PPM/° K. Onemetallic material believed suitable for use in frame/spacers 2014 thatwill be bonded to silicon (Si) substrates is the alloy known as “LowExpansion 39 Alloy,” developed by Carpenter Specialty Alloys. LowExpansion 39 Alloy is understood to have a composition (weight percent;nominal analysis) as follows: about 0.05% C, about 0.40% Mn, about 0.25%Si, about 39.0% Ni, and the balance Fe. Low Expansion 39 Alloy has a CTEthat is understood to range from about 2.3 PPM/° K over the interval of25° C. to 93° C., to about 2.7 PPM/° K at 149° C., to about 3.2 PPM/° Kat 260° C., and to about 5.8 PPM/° K at 371° C.

Similarly, it is recognized that gallium arsenide (GaAs) of the typeused for WLP wafer substrates has a nominal CTE of about 5.8 PPM/° K.Based on material suppliers' data, Kovar alloy is understood to have aCTE ranging from about 5.86 PPM/° K at 20° C. to about 5.12 PPM/° K at250° C. Thus, Kovar alloy appears to be a good choice for frame/spacers2014 that will be bonded to GaAs substrates. Another material believedsuitable for frame/spacers 2014 that will be bonded to GaAs substratesis the alloy known as Silvar™, developed by Texas Instruments Inc.'sMetallurgical Materials Division, of Attleboro, Mass. It is understoodthat Silvar™ is a derivative of Kovar with CTE characteristics closelymatched to GaAs devices.

With regard to the window/lens for WLPs, it is believed that all of theglasses previously described for use in the manufacture of individualand multiple window assemblies having Kovar frames, e.g., Corning 7052,7050, 7055, 7056, 7058 and 7062, Kimble (Owens Corning) EN-1, KimbleK650 and K704, Abrisa soda-lime glass, Schott 8245 and Ohara CorporationS-LAM60, will be suitable for the window/lens 2016 of WLPs having a GaAssubstrate 2006. Pyrex glasses and similar formulations are believedsuitable for the window/lens 2016 of WLPs having silicon substrates2006. The properties of Pyrex, per the Corning website, are: softeningpoint of about 821° C., annealing point of about 560° C., strain pointof about 510° C., working point of about 1252° C., expansion (0-300° C.)of about 32.5×10⁻⁷/° C., density of about 2.23 g/cm³, Knoop hardness ofabout 418 and refractive index (at 589.3 nm) of about 1.474.

Referring now to FIG. 22, there is illustrated a semiconductor wafer2202 having a plurality of micro-devices 2204 formed thereupon. It willbe appreciated that methods for the production of multiple micro-deviceson a single semiconductor wafer are conventional. Heretofore, however,when the micro-devices 2204 are of the type which must be hermeticallypackaged prior to use, e.g., MEMS, MOEMS, opto-electronic or opticaldevices, it has been standard practice in the industry to first“individuate” or “singulate” the micro-devices, e.g., by cutting-apart,dicing (apart) or breaking-apart the wafer 2202 into sections having,typically, only a single micro-device on each, and then packaging theindividuated micro-devices in separate packages. Now, in accordance withadditional embodiments of the current invention, multiple micro-devicesmay be individually hermetically packaged, or hermetically packaged inmultiples, in a WLP prior to individuation or singulation of thesubstrate wafer. This process is referred to as multiple simultaneouswafer-level packaging, or “MS-WLP.”

Referring now to FIGS. 23 through 29, there is illustrated one methodfor MS-WLP of micro-devices. Briefly, this method includes the steps of:a) preparing a first frame-attachment area on the surface of asemiconductor wafer substrate having a plurality of micro-devices, thefirst frame-attachment area having a plan circumscribing individual (ormultiple) micro-devices on the substrate; b) preparing a secondframe-attachment area on the surface of a window (i.e., a sheet oftransparent material), the second frame-attachment area having a plansubstantially corresponding to the plan of the first frame-attachmentarea; c) positioning a frame/spacer between the substrate and thewindow, the frame/spacer having a plan substantially corresponding to,and in register with the plans of the first and second frame-attachmentareas, respectively; and d) hermetically bonding the substrate,frame/spacer and window together so as to encapsulate the micro-device.If applicable, solder preforms or other materials including, but notlimited to, innerlayers of interlayers for diffusion bonding, are alsopositioned between the frame/spacer and the window and/or substratebefore bonding.

Referring now specifically to FIG. 23, the frame-attachment area 2302 ofsemiconductor wafer 2202 has been prepared by depositing metallizedlayers onto the surface of the wafer substrate completely around (i.e.,circumscribing) each micro-device 2204. In the embodiment shown, theprepared frame-attachment area 2302 includes a rectangular gridconsisting of double-width metallized rows 2304 and columns 2306(interposed between the micro-devices 2204) surrounded by single-widthouter rows 2308 and columns 2310. The composition and thickness of themetallized layers in frame-attachment area 2302 may be any of thosepreviously described for use in preparing the sheet seal-ring area 318as set forth in Examples 1-96.

Referring now to FIG. 24, there is illustrated a MS-WLP frame/spacer2402 for attachment between the wafer 2202 and the window sheet 2602 ofthe MS-WLP assembly. It will be appreciated that in this embodiment, theMS-WLP frame/spacer 2402 has double-width row members 2404 and columnmembers 2406 surrounded by single-width outer row members 2408 andcolumn members 2410, resulting in a plan which corresponds substantiallywith the plan of the frame-attachment area 2302 on the wafer substrate2202. As will be further described below, the purpose of thedouble-width row and column members 2404 and 2406 is to allow room forcutting the frame during singulation of the MS-WLP assembly afterbonding. It will be appreciated that, in other embodiments, the MS-WLPframe/spacer may have a different configuration. In this embodiment, theMS-WLP frame/spacer 2402 is formed of a metal alloy having a CTEsubstantially matched to the CTE of wafer substrate, however, in otherembodiments the frame/spacer may be formed of non-metallic materials aspreviously described. Also as previously described, the frame/spacer2402 will preferably be plated or metallized to facilitate the bondingprocess.

Referring now to FIGS. 25 a-25 d, there are illustrated details of apreferred configuration for the frame/spacer 2402. FIG. 25 a shows anenlarged plan view of a portion of the double-width column member 2406and FIG. 25 b shows an end view of the same portion. It will beappreciated that the row members 2404 of the frame/spacer 2402preferably have a similar configuration. The member 2406 is formed tohave a “groove” 2502, or reduced thickness area, running along thecentral portion of each member, i.e., between the adjacent micro-devicesin the completed MS-WLP assembly. As will be further described below,the groove 2502 facilitates cutting apart of the MS-WLP assembly duringsingulation of the packaged micro-devices. After being cut apart alongthe groove 2502, the frame member 2406 will be divided into twosingle-width members 2504, each one having the configuration shown inFIGS. 25 c and 25 d. During assembly, the grooved side 2505 of the framemember is preferably positioned against the wafer substrate 2202, whilethe ungrooved side 2505 is positioned against the window sheet.

Referring now to FIG. 26, there is illustrated a MS-WLP window sheet2600 for attachment to the MS-WLP frame/spacer 2402. The window sheet2600 is formed of glass or other transparent material having a CTEcompatible with the other principal components of the assembly aspreviously described. At least the inner side (i.e., the side that willbe inside the hermetic envelope) of the sheet 2600, and preferably bothsides, must be optically finished. Any desired optical or protectivecoatings are preferably present on at least the inner side, andpreferably on both sides, of the sheet 2600 at this point. However, ifthe sheet 2600 is attached to only the frame/spacer 2402 in the first oftwo bonding operations, then the optical or protective coatings may beapplied prior to the second, later bonding step of attaching the windowassembly to the wafer. A frame-attachment area 2602 is prepared on theMS-WLP window sheet 2600 so as to circumscribe a plurality of windowapertures 2603 that will ultimately be aligned with the micro-devices2204 in the final MS-WLP assembly. In the embodiment shown, the preparedframe-attachment area 2602 takes the form of metallic layers depositedon the sheet 2600 in a rectangular grid consisting of double-width rows2604 and columns 2606 surrounded by single-width outer rows 2608 andcolumns 2610. This results in a plan for the frame-attachment area 2602,which corresponds substantially with the plan of the frame/spacer 2402.The composition and thickness of the metallized layers 2604, 2606, 2608and 2610 in the frame-attachment area 2602 may be any of thosepreviously described for use in preparing the sheet seal-ring area 318of the “stand-alone” windows set forth in Examples 1-96.

In some embodiments, the inner surface of the window sheet 2600 may bescribed, e.g., with a diamond stylus, through each portion of theframe-attachment area 2602 to facilitate breaking apart of the MS-WLPassembly during singulation. The scribing of the window sheet 2600 wouldobviously be performed prior to bonding or joining it to theframe/spacer 2402. Where the frame/spacer 2402 includes grooved memberssuch as those illustrated in FIGS. 25 a-25 b, then the scribe lines onthe sheet 2600 will preferably be in register with the grooves 2502 ofthe frame members in the MS-WLP assembly.

Referring now to FIG. 27, there is illustrated a side view of a completeMS-WLP assembly 2700. It will be appreciated that the proportions ofsome of the components shown in FIG. 27 (e.g., the thicknesses of themetallic layers) may be exaggerated for purposes of illustration. Theframe/spacer 2402 is positioned between the wafer substrate 2202 (withassociated micro-devices 2204) and the window sheet 2600, with the plansof the frame-attachment areas 2302 and 2602 being substantially inregister with the plan of the frame/spacer 2402 such that eachmicro-device or set of micro-devices 2204 is positioned beneath a windowaperture area 2603 of the window sheet. Of course, if the assembly 2700is bonded using solder technology, then solder preforms (not shown)having a plan substantially corresponding with the frame-attachmentareas 2302 and 2602 are also positioned between the frame/spacer 2402and the frame-attachment areas prior to bonding. Also, if innerlayers orinterlayers are used in conjunction with diffusion bonding, theseinterlayers (not shown) having a plan substantially corresponding withthe frame-attachment areas 2302 and 2602 are also positioned between theframe/spacer 2402 and the frame-attachment areas prior to bonding. Anyof the previously described bonding technologies may be used toeffectuate the bond between the components. The MS-WLP assembly 2700will look essentially the same before bonding and after bonding (exceptfor incorporation into the bond area of any solder preforms).

After bonding, the MS-WLP assembly 2700 is cut apart, or singulated, toform a plurality of hermetically sealed packages containing one or moremicro-devices each. There are several options carrying out thesingulation procedure. However, since the window sheet 2600, frame 2402and wafer substrate 2202 are bonded together, simply scribing andbreaking the window sheet (as was done for the multiple stand-alonewindow assemblies) is not practical. Instead, at least the window sheet2600 or the wafer substrate 2202 must be cut. The remaining portion maythen either be cut, or scribed and broken. It is believed that the bestresult will be obtained by cutting the wafer substrate 2202 using awafer-dicing saw, and then either scribing-and-breaking the window sheet2600, or cutting the window sheet using a similar dicing saw.

Referring now to FIG. 28, there is illustrated one option forsingulation of a MS-WLP assembly. The MS-WLP assembly 2800 shown in FIG.28 is similar in most respects to the assembly 2700 shown in FIG. 27,however, in this case the window sheet 2600 was pre-scribed (as denotedby reference number 2802) through the metallic layers 2406, if employed(and also layers 2404 running perpendicular thereto, also if employed)of the interior frame-attachment areas. After bonding, the assembly 2800is cut from the outer side of the wafer substrate 2202 (as indicated byarrow 2804) completely through the substrate and into the groove 2502 ofinterior frame/spacer members 2606 (and also members 2604 runningperpendicular thereto). The cut 2804 does not, however, continue throughthe window sheet 2600. Instead, after the wafer substrate 2202 and frame2402 are cut, the window sheet 2600 is broken by bending it along thepre-scribed lines 2802. The assembly 2800 may be first broken into rows,then each row broken into individual packages along the column lines, orvice versa. In one variation of this method, the window sheet 2600 isnot pre-scribed, but instead is scribed through the kerf 2806 formed bycutting through the wafer substrate 2202 and frame 2402. It will beappreciated that this scribing must be sufficiently forceful to cutthrough the remaining portion of the frame member 2406 and metalliclayers 2606 under the groove 2502. The assembly is then broken intoindividual packages along the scribe lines as before.

Referring now to FIG. 29, in another variation, a MS-WLP assembly 2900is individuated by simply cutting completely through the wafer substrate2202, frame/spacer 2402 and window sheet 2600 between each micro-device2204 as indicated by arrow 2902. The result is a plurality ofindividually WLP micro-devices 2904. The individuating cuts may be madefrom either the window side or the substrate side, however, it may benecessary to protect the outer surface of the window sheet (e.g., withmasking tape, etc.) to protect it from damage during the sawingoperation.

When electrical-resistance heating (“ERH”) is used to facilitatediffusion bonding or soldering of the components of a MS-WLP assembly,the electrical current is typically applied so that it flows throughboth the window/frame junction and the frame/substrate junctionsimultaneously. To facilitate this ERH heating, the configuration of theMS-WLP assembly may be modified to provide “sacrificial” metallizedareas (i.e., areas that will be discarded later) on the window sheet andwafer substrate for placement of ERH electrodes. Preferably, theelectrode placement areas on the substrate and window will be accessiblefrom directions substantially perpendicular to the wafer.

Referring now to FIG. 30, there is illustrated a wafer 3000 similar inmost respects to the wafer 2002 of FIG. 23, i.e., having a plurality ofmicro-devices 2204 formed thereon and a metallized frame-attachment area3002 formed thereon so as to surround the micro-devices. In this case,however, the wafer 3000 further includes a metallized electrodeplacement pad 3004 positioned at one end of the wafer. The electrodeplacement pad 3004 is in electrical contact with the metallized layers2304, 2306, 2308 and 2310 of the frame-attachment area 3002.

Referring now to FIG. 31, there is illustrated window sheet 3100 similarin most respects to the sheet 2600 of FIG. 26, i.e., having a metallizedframe-attachment area 3102 formed thereon so as to surround the windowaperture areas 2603 on the sheet. In this case, however, the sheet 3100further includes a metallized electrode placement pad 3104 positioned atone end of the sheet. The electrode placement pad 3104 is in electricalcontact with the metallized layers 2604, 2606, 2608 and 2610 of theframe-attachment area 3102.

Referring now to FIG. 32, there is illustrated a MS-WLP assembly 3200 inaccordance with another embodiment. The components of the assembly 3200are positioned such that the wafer substrate 3000 and the window sheet3100 are adjacent to the frame/spacer 2402, but the respectivemetallized electrode placement pads 3004 and 3104 overhang on oppositesides of the assembly. This configuration provides unobstructed accessto the pads 3004 and 3104 in a direction perpendicular to the wafer (asdenoted by arrows 3202), allowing easy attachment of electrodes for ERHprocedures.

During bonding of WLP assemblies, there are two bonds that shouldtypically occur simultaneously: the junction between the frame/spacerand the window sheet and the junction between the frame/spacer and thewafer substrate. As was described previously, however, the window mayfirst be bonded only to the frame, and later, using ERH, thewindow/frame assembly can be attached to the substrate of the device. Aswas previously described in the process for the manufacturing ofstand-alone window assemblies, the configuration of the metal frame andplacement of ERH electrodes may be critical for even heating using ERHheating techniques. Similarly, for MS-WLP devices, the metallizationpatterns and ERH electrode placement locations on the wafer substrateand the window sheet may be important to achieving even heating.Therefore, the size/shape of the frame including possibly excess orsacrificial features, and the metallization patterns on both the windowsheet and the wafer substrate should be concurrently designed, modeled(e.g., using software simulation) and prototyped to ensure even heatingof the bonded surfaces/features.

It will be appreciated that the previous embodiment describes a methodfor manufacturing MS-WLP assemblies which is suited for micro-deviceshaving opposite-side electrical connection pads. Referring now to FIG.33, there is illustrated a micro-device having same-side electricalconnections. The micro-device 3300 is disposed on one side of asemiconductor substrate 3302. A plurality of vias 3304 run from theactive areas of the micro-device, through the substrate, and to aplurality of connection pads 3306 located on the same side of thesubstrate. Obviously, the electrical connection pads 3306 must beaccessible even after the micro-device 3300 has been sealed within itshermetic package. In the following embodiment, there is presentedanother method for manufacturing MS-WLP assemblies suited for use withsuch micro-devices with same-side connections.

Referring now to FIG. 34, there is illustrated a wafer 3402 having aplurality of micro-devices 3300 formed thereupon, each micro-devicehaving one or more sets 3403 of associated same-side connection pads3306. In accordance with this embodiment, the multiple micro-devices3300 are individually hermetically packaged in a WLP prior toindividuation of the substrate wafer 3402, however the same-sideelectrical connection pads 3306 remain accessible. The steps of thisembodiment are similar in many respects to those of the previousembodiment, except for the changes described below.

Referring now to FIG. 35, the frame-attachment area 3502 of thesemiconductor wafer 3402 is first prepared, in this case by depositingmetallized layers onto the surface of the wafer substrate circumscribingeach micro-device 3300. In the embodiment shown, the preparedframe-attachment area 3502 includes three “ladder-shaped” grids 3503,each consisting of double-width metallized rows 3504 (i.e., the “rungs”of the ladder) and single-width columns 3506 (the “sides” of the ladder)connected by buss strips 3508 at each end. The composition and thicknessof the metallized layers in frame-attachment area 3502 may be any ofthose previously described for use in preparing the sheet seal-ring areaor frame attachment areas.

Referring now to FIG. 36, there is illustrated a MS-WLP frame/spacer3602 for attachment between the wafer 3402 and the window sheet 3702(FIG. 37) of the MS-WLP assembly. It will be appreciated that in thisembodiment, the MS-WLP frame/spacer 3602 is configured into multipleladder shaped portions 3603, each portion having double-width rungmembers 3604 and single-width side members 3606 that are configured tohave a plan substantially corresponding to the ladder-shaped plans 3503of the frame-attachment area 3502 on the wafer substrate 3402. Theladder-shaped portions 3603 are attached to, and held in relativeposition to one-another by, connecting members 3608 located at oppositeends of the frame/spacer 3602. As in the previous embodiment, thedouble-width members 3604 allow room for cutting the frame 3602 betweenmicro-devices during singulation of the MS-WLP assembly (i.e., afterbonding). In a preferred embodiment, the double-width members may have agrooved cross-section (e.g., similar to that shown in FIGS. 25 a and 25b) to facilitate their cutting apart. It will be appreciated however,that in other embodiments the MS-WLP frame/spacer may have a differentconfiguration. In this embodiment, the MS-WLP frame/spacer 3602 isformed of a metal alloy having a CTE substantially matched to the CTE ofthe wafer substrate; however, in other embodiments the frame/spacer maybe formed of non-metallic materials as previously described. Also aspreviously described, the frame/spacer 3602 will preferably be plated ormetallized to facilitate the subsequent bonding process.

Referring now to FIG. 37, there is illustrated a MS-WLP window sheet3700 for attachment to the MS-WLP frame/spacer 3602. The window sheet3700 is formed of glass or other transparent material having a CTEcompatible with the other principal components of the assembly aspreviously described. At least the inner side (i.e., the side that willbe inside the hermetic envelope) of the sheet 3700 (and preferably bothsides) is optically finished, and any desired optical or protectivecoatings are in place on the inner side. Either before or after anydesired optical or protective coatings are in place on the inner side ofsheet 3700 (and preferably both sides), a frame-attachment area 3702 isprepared on the MS-WLP window sheet 3700 so as to circumscribe aplurality of window apertures 3705 that will ultimately be aligned withthe micro-devices 3300 in the final MS-WLP assembly. In the embodimentshown, the prepared frame-attachment area 3702 includes metallic layersdeposited on the sheet 3700 in multiple ladder-shaped portions 3703,each portion including double-width rung members 3704 and single-widthside members 3706. Each ladder portion 3703 has a plan, whichcorresponds substantially with the plan of the ladder portions 3603 ofthe frame/spacer 3602. The methods and procedures for preparation of thewindow sheet 3700, including the composition and thickness of themetallized layers 3704 and 3706 in the frame-attachment area 3702, maybe any of those previously described for use in preparing the sheetseal-ring area 318 of the “stand-alone” window assemblies or the frameattachment areas 2602 of the window sheet 2600 of the MS-WLP.

In the embodiment illustrated in FIG. 37, the metallized layers ofwindow sheet 3700 extend beyond the ladder-shaped portions 3703, andincluded additional portions configured to facilitate electricresistance heating (ERH). These additional portions include electrodeattachment portions 3708 and bridge portions 3710, both of which areelectrically connected to the metallized layers 3704 and 3706 of theladder portions 3703. The configuration, e.g., placement and thickness,of these electrode attachment portions 3708 and bridge portions 3710 areselected to manage the flow of ERH current through the interfacesbetween the metallized portions of the window sheet 3700 and theframe/spacer 3602, and through the interface between the frame/spacer3602 and the metallized portions of the substrate 3402, therebycontrolling the heating at these interfaces during ERH-facilitatedbonding operations.

As in previous embodiments, the inner surface of the window sheet 3700may be scribed, e.g., with a laser or diamond stylus, through eachportion of the frame-attachment area 3702 to facilitate breaking apartof the MS-WLP assembly during singulation. Where the frame/spacer 3602includes grooved members such as those illustrated in FIGS. 25 a-25 b,then the scribe lines on the window sheet 3700 will preferably be inregister with the grooves 2502 of the frame members in the MS-WLPassembly.

Referring now to FIG. 38, there is illustrated a top view of a completeMS-WLP assembly 3800 including the wafer substrate 3402, frame/spacer3602 and window sheet 3700 stacked on one another such that theladder-shaped areas 3503, 3603 and 3703 of each respective component aresubstantially in register with one another, and such that each of themicro-devices 3300 is positioned beneath a window aperture area 3705 ofthe window sheet. It will be appreciated that in this embodiment, theconfigurations of the wafer 3402 and window sheet 3700 are complementaryto facilitate the placement of ERH electrodes. Specifically, theportions of the wafer 3402 having the metallized buss strips 3508project past the edges of the sheet 3700 (when viewed from above),allowing one set of ERH electrodes to make contact from verticallyabove, while the portions of the sheet having the metallized contactportions 3708 project past the edge of the wafer (when viewed frombelow), allowing another set of ERH electrodes to make contact fromvertically below.

Of course, if the assembly 3800 is to be bonded using solder technology,then solder preforms (not shown) having a plan substantiallycorresponding with the frame-attachment areas are also positionedbetween the frame/spacer 3602 and the frame-attachment areas of thewindow sheet 3700 and substrate 3402 prior to bonding. Any of thepreviously described bonding technologies may be used to effectuate thebond between the components. If the assembly 3800 is to be bonded usingdiffusion bonding technology, then when using interlayer preforms (notshown), these preforms will have a plan substantially corresponding withthe frame-attachment areas and are also positioned between theframe/spacer, 3602 and the frame-attachment areas of the window sheet3700 and/or between the frame/spacer 3602 and substrate 3402 prior tobonding. The MS-WLP assembly 3800 will look essentially the same beforebonding and after bonding (except for incorporation into the bond areaof any solder preforms or interlayers for diffusion bonding).

After bonding, the window sheet 3700 of the assembly 3800 may be viewedas including primary strip portions 3802, which overlie the plurality ofencapsulated micro-devices 3300, secondary strip portions 3804, whichare interposed between the primary strips and overlie rows ofnon-encapsulated contact pads 3403, and end strip portions 3806, whichare disposed at each end of the window sheet and also overlie rows ofnon-encapsulated contact pads 3403. During singulation of the assembly3800, the secondary and end strip portions 3804 and 3806, respectively,of the window sheet are cut away and discarded, these parts beingessentially “sacrificial.” Further during singulation, the substrate3402 is divided along cut lines (denoted by arrows 3808) between thecolumns of micro-devices 3300 and contact pads 3403 to form multi-unitstrips. The separating of the window sheet may be performed using saws,lasers or other conventional means, while the dividing of the substratemay be performed using saws, lasers, or by snapping along a score line.

Referring now to FIGS. 39 and 40, singulation of the MS-WLP assembly3800 is illustrated. Referring first to FIG. 39, there is illustrated amulti-unit strip 3900 which has been separated from the MS-WLP assembly3800. The multi-unit strip 3900 includes a plurality of micro-devices3300 on a portion 3902 of the original wafer substrate 3402, themicro-devices being encapsulated within adjacent hermetic envelopeshaving one or more micro-devices under each window portion 3705 of theoriginal window sheet, but with their associated electrical contact pads3403 being non-encapsulated. The multi-unit strip 3900 is further cutapart, or singulated, along cut lines 3904, which in this embodimentcorresponds to the center of the frame members 3604 separating theadjacent hermetic envelopes. The result is a plurality of discretehermetically sealed WLP packages containing one or more micro-devicesunder each window portion 3705. An example of an individual WLP package4000 produced by this method is illustrated in FIG. 40.

During the singulation of multi-unit strips 3900, at least the windowsheet 3700 or the wafer substrate portion 3902 must be cut. Theremaining portion may then either be cut, or scribed and broken. It isbelieved that the best result will be obtained by cutting the wafersubstrate portion 3902 using a wafer-dicing saw, and then eitherscribing-and-breaking the window sheet 3700, or cutting the window sheetusing a similar dicing saw.

When making multiple cover assemblies simultaneously, as previouslydescribed and illustrated (e.g., in FIGS. 15 a-19 f), or making multiplewafer-level packages simultaneously, as previously described andillustrated (e.g., in FIGS. 22-40), the frame sidewalls between adjacentframe apertures may include reduced cross-sectional thickness areas tofacilitate the singulation (i.e., dividing) of the joined multiple-unitassembly into individual window assemblies or individual wafer-levelpackages. As best seen in FIGS. 15 a-16 b, 17 b, 25 a-25 b, 27 and 32,this reduced cross-sectional thickness area may take the form of aV-shaped notch formed in the frame sidewalls between adjacent frameapertures. It will be appreciated, however, that alternative framedesigns may substituted for those previously illustrated to provide foreasier frame fabrication and/or easier singulation of a joinedmultiple-unit assembly into individual window assemblies or individualwafer-level packages.

Referring now to FIG. 41, there is illustrated (in side elevation view)a portion of a multiple simultaneous wafer-level packaging assembly 4100incorporating one alternative frame design. It will be appreciated thatthe assembly 4100 is shown prior to singulation into individualpackages. It will further be appreciated that the assembly 4100 issimilar in most ways to the MS-WLP assemblies previously described andillustrated in FIGS. 27-29. The assembly 4100 includes a frame 4102hermetically joined to a wafer substrate 4104 having micro-devices 4106formed (and/or mounted) thereupon and to a transparent window sheet4108, thereby forming a plurality of individual hermetically sealedunits 4110 that can be singulated (e.g., along lines 4112) between theadjacent frame apertures 4114 to form discrete hermetically sealedpackages. Diffusion bonding, or any of the other previously describedbonding technologies may be used to effectuate the hermetic seal betweenthe frame 4102, substrate 4104 and sheet 4108. As in previous designs,when viewed in plan (i.e., from above as in FIG. 24), the sidewalls ofthe frame 4102 circumscribe the frame apertures 4114 and have an upperside plan which substantially corresponds to the plan of the predefinedframe attachment areas of the sheet 4108. Also as in previous designs,when viewed in elevation, the sidewalls disposed between adjacent frameapertures 4114 include reduced cross-sectional thickness areas. However,in this embodiment, the reduced cross-sectional thickness areas of theframe 4102 take the form of a relatively thin connecting tab 4116extending between two relatively thick sidewall members 4118. In FIG.41, the undivided interior frame sidewall is denoted by reference number4120.

The connecting tab 4116 of the sidewall 4120 is characterized by arelatively constant vertical thickness T_(CT), which is significantlysmaller than the overall vertical thickness T_(SW) of the adjacentsidewall members 4118. Preferably, the value of connecting tab thicknessT_(CT) is less than 25% of the value of the overall sidewall memberthickness T_(SW). More preferably, the value of connecting tab thicknessT_(CT) is less than 10% of the value of sidewall member thicknessT_(SW), and in some cases the value of T_(CT) is less than 5% of thevalue of T_(SW). During fabrication of multiple-unit assemblies, therelatively thin connecting tabs 4116 of this design are sufficientlystrong to maintain the structural integrity of the overall frame 4102.However, during singulation, the relatively thin connecting tabs 4116can be severed with little chance of damaging or distorting theadjacent, relatively thick sidewall members 4118, or of damaging theunit's hermetic seal. In addition, the relatively thin connecting tabs4116 make it easier for the singulating device, e.g., dicing saw, laser,etc., to cut through the frame's reduced cross-section area, andsometimes also the substrate 4104 and/or window sheet 4108 in the sameoperation.

Referring now to FIGS. 42 a-42 e, there are illustrated severalalternative frame designs which can be used for making either multiplecover assemblies simultaneously or multiple wafer-level packagessimultaneously. In each figure, there is shown a cross-sectional view ofan undivided interior sidewall 4120 having a reduced cross-sectionalthickness area comprising a relatively thin connecting tab 4116extending between two relatively thick sidewall members 4118. Thesidewall 4120 is designed to be singulated along a line denoted by arrowS. It will be understood that the entire frame 4102 will comprise manysuch sidewalls laid out in a grid pattern to form discrete apertures.The connecting tab 4116 may be positioned at any desired verticalposition between the sidewall members 4118, including, but not limitedto, at the top (FIG. 42 a), middle (FIG. 42 c), bottom (FIG. 42 e),upper or lower intermediate positions (FIGS. 42 b and 42 d). It will beappreciated that illustrating all possible vertical locations for theconnecting tab 4116 would be impractical, but nonetheless such designsfall within the scope of the current invention, provided that theconnecting tab has a relatively constant vertical thickness T_(CT) thatis significantly smaller than the overall vertical thickness T_(SW) ofthe adjacent sidewall members 4118, preferably less than 25% of T_(SW),more preferably less than 10% of T_(SW) and sometimes less than 5% ofT_(SW).

Referring now to FIGS. 43 a-43 e, additional frame designs areillustrated by showing an undivided sidewall 4120 in the same fashion asthose of FIGS. 42 a-42 e. While a sidewall 4120 may have only a singleconnecting tab 4116 extending between the sidewall members 4118 (FIG. 43a), it may also have two (FIGS. 43 b and 43 c), three (FIG. 43 d), four(FIG. 43 e), or even more connecting tabs extending between the sidewallmembers. Further, these multiple connecting tabs 4116 may be positionedat any desired vertical position between the sidewall members 4118,including, but not limited to, at the top and bottom (FIG. 43 b) or atintermediate positions (FIG. 43 c). It will be appreciated thatillustrating all possible numbers of connecting tabs 4116 and allpossible vertical locations for the connecting tabs would beimpractical, but nonetheless such designs fall within the scope of thecurrent invention, provided that each connecting tab has a relativelyconstant vertical thickness T_(CT) that is significantly smaller thanthe overall vertical thickness T_(SW) of the adjacent sidewall members4118, preferably less than 25% of T_(SW), more preferably less than 10%of T_(SW) and sometimes less than 5% of T_(SW).

Referring now to FIGS. 44 a-44 e, further frame designs are illustratedby showing an undivided sidewall 4120 in the same fashion as those ofFIGS. 42 a-43 e. While the sidewall members 4118 may be generallyrectangular in cross-sectional configuration (as shown in FIGS. 42 a-43e), this is not required. Rather, the sidewall members 4118 may havecross-sectional configurations which taper (i.e., narrow) as they getvertically farther from the location of the connecting tab 4116. Theconnecting tab 4116 may still be positioned at any desired verticalposition between the sidewall members 4118, including, but not limitedto, at the top (FIG. 44 a), middle (FIG. 44 c), bottom (FIG. 44 e),upper or lower intermediate positions (FIGS. 44 b and 44 d). Thisresults in some designs with tapers in a single direction (e.g., FIGS.44 a and 44 e) and some with tapers in two directions (e.g., FIGS. 44b-44 d). The tapered sidewalls 4118 of these designs may result inimproved manufacturing qualities, e.g., where the frame is molded orstamped and must release cleanly from the tooling. It will beappreciated that illustrating all possible vertical locations for theconnecting tab 4116 and taper configurations for the sidewall members4118 would be impractical, but nonetheless such designs fall within thescope of the current invention, provided that at least one of thesidewall members has a tapered cross-sectional configuration andprovided that the connecting tab has a relatively constant verticalthickness T_(CT) that is significantly smaller than the overall verticalthickness T_(SW) of the adjacent sidewall members, preferably less than25% of T_(SW), more preferably less than 10% of T_(SW) and sometimesless than 5% of T_(SW).

Referring now to FIGS. 45 a-45 f, still further frame designs areillustrated by showing an undivided sidewall 4120 in the same fashion asthose of FIGS. 42 a-44 e. In these designs, single, double, or multipleconnecting tabs 4116 extend between sidewall members 4118 havingcross-sectional configurations with single, double or multiple tapers.For example, the sidewall 4120 of FIG. 45 a has a single connecting taband a single direction taper, while the design of FIG. 45 f has multiple(i.e., three) connecting tabs and multiple (i.e., six) tapers. Some ofthe more complex configurations may be unsuited for manufacture byconventional stamping or molding, and must instead be formed using otherprocesses such as extrusion or photo-chemical machining (furtherdescribed below). It will be appreciated that illustrating all possiblecross-sectional configurations for these sidewalls 4120 would beimpractical, but nonetheless such designs fall within the scope of thecurrent invention, provided that at least one of the sidewall membershas a tapered cross-sectional configuration and provided that eachconnecting tab has a relatively constant vertical thickness T_(CT) thatis significantly smaller than the overall vertical thickness T_(SW) ofthe adjacent sidewall members, preferably less than 25% of T_(SW), morepreferably less than 10% of T_(SW) and sometimes less than 5% of T_(SW).

Referring now to FIGS. 46 a-46 d, portions of several interior sidewalls4120 are shown in plan (i.e., from above) to better illustrate theconfigurations of the connecting tabs 4116. It will be understood thatthe sidewalls 4120 extend beyond what is shown in the figures to formthe complete frame grid. When seen in plan, the paired sidewall members4118 of an interior sidewall 4120 typically run parallel to one another,but the connecting tabs 4116 may extend continuously between thesidewall members, or they may be intermittent. In addition, theconnecting tabs 4116 may be perforated with longitudinal or lateralperforations. For example, in FIG. 46 a, an interior sidewall (denoted4120′) has a connecting tab 4116 that is a solid piece extending betweenthe two sidewall members 4118. In this embodiment, the tab 4116 is notcontinuous everywhere between the sidewall members 4118, but rather hasa fixed length L. Additional similar discrete connecting tabs 4116 maybe provided intermittently at other locations between the sidewallmembers 4118 as required. In contrast, another interior sidewall(denoted 4120″) in FIG. 46 b has a connecting tab 4116 that extendscontinuously between the two sidewall members 4118. In this embodiment,longitudinal perforations 4602 are formed in the connecting tab alongeach sidewall member to facilitate separation of the sidewall membersduring singulation. In FIG. 46 c, a third interior sidewall (denoted4120′″) is shown. The connecting tab 4116 of the sidewall 4120′″ has afixed length L, and it also has longitudinal perforations 4604, thistime formed along the center of the tab to facilitate separation of thesidewall members 4118 during singulation. In FIG. 46 d, a fourthinterior sidewall (denoted 4120″″) is shown. The connecting tab 4116 ofthe sidewall 4120″″ has a fixed length L and perforations 4606 formedlaterally across the tab from one sidewall member to the other. Solidtabs will preferably be cut apart by laser or by mechanical (e.g.,sawing, shearing, etc.) means. Perforated tabs may be cut apart insimilar fashion, but may also be separated by twisting or repeatedbending along the perforation.

Frames for cover assemblies or wafer-level packages, whether forindividual or for multiple units, may be fabricated using photo-chemicalmachining (also known as “PCM”). Photo-chemical machining is a materialremoval process that uses an etchant (e.g., acid) to “machine” precisionparts without cutting. PCM is typically used for forming metal parts,although it can also be used for non-metallic materials (e.g., glasses,semiconductors, ceramics, etc.) with a suitable etchant. Briefly, thesilhouette of the desired part is first photographically imaged on asheet of metal or other material treated with a photo-sensitive resistmaterial. After processing, the unwanted material (i.e., that notprotected by the resist material) is etched away, leaving a finishedpart that duplicates the original silhouette and is stress-free,burr-free and as flat as the parent sheet from which it was etched.Because of certain characteristics of the etching process, the maximumsheet thickness that can be satisfactorily processed using PCM islimited. However, when frames thicker than this maximum sheet thicknessare desired, multi-layer frame assemblies may be used as describedbelow.

In yet another aspect, multi-layer frame assemblies (also known aslaminated frames) are fabricated from a plurality of thin, pre-shapedsheets that are stacked together and bonded into a single unit frame.Each sheet may be pre-formed to have the silhouette of the desired crosssection for its respective position in the finished frame, therebyreducing or eliminating the need for further processing after bonding.The sheets may be formed by PCM, stamping, cutting, molding or otherknown processing methods. The sheets in a multi-layer frame may be madeof any of the frame materials disclosed herein. Diffusion bonding (i.e.,thermal compression bonding) may be used to laminate the sheetstogether, as well as other processes such as conventional soldering,brazing, etc. Multi-layer frame assemblies can also be used to fabricateframes having more complex structures, e.g., the flanged frame shown inFIG. 20 a, by using different silhouettes for different layers.

It will be appreciated that the various layers of a multi-layer frame donot necessarily need to be made of the same material. It is onlynecessary that the materials of directly adjacent sheets be hermeticallybondable to one another. Thus, various metals, non-metals, orcombinations of metals and non-metals may be laminated together to forma multi-layer frame. Such “mixed-material” laminated frames allow themechanical, thermal, electrical and/or chemical properties of the frameto be customized. For example, a multi-layer frame can be made withdifferent materials on the upper and lower surfaces to promote bondingto different window and substrate materials. In another example, bylaminating sheets of materials having different CTEs, the overall CTE ofthe resulting multi-layer frame may be customized.

Referring now to FIGS. 47 and 48, there is illustrated is a multi-layerframe assembly fabricated from sheets made by photo-chemical machining(PCM). While PCM is used for this example, the same general processwould be used, with only minor changes, if the sheets were fabricatedusing the alternative methods previously described. FIG. 47 shows a planview of the assembly 4700, while FIG. 48 shows a cross-sectionalelevation view. The assembly 4700 of this embodiment includes fourlayers, denoted 4701, 4702, 4703 and 4704. Each layer is fabricated byPCM, and includes a plurality of individual frames 4705, each framehaving a continuous sidewall 4706 circumscribing and defining a frameaperture 4708. It will be understood that the plans of the sidewalls4706 on each layer 4701, 4702, 4703 and 4704 of the assembly 4700 willat least partially overlap the plans of sidewalls of the adjacent layersall the way around each of the frame apertures 4708, and the plan of theuppermost layer 4701 will also substantially correspond to the plan ofthe frame attachment areas on the window sheet (not shown) to which theframe assembly will be joined. In the embodiment illustrated, the plansof the sidewalls 4706 on each layer 40701, 4702, 4703 and 4704 aresubstantially identical, however, such identity of structure is notrequired for all embodiments (e.g., a flanged frame would have at leastsome layers with plans that are non-identical). The frame sidewalls 4706disposed between two frame apertures 4708 in each sheet are held inplace by connecting tabs 4710 similar to those shown in FIGS. 46 a and46 c. In this case, however, the connecting tabs 4710 will usually(although not always) have a vertical thickness that is the same as thethickness of the original sheet. To facilitate later singulation, theconnecting tabs 4710 for the different layers 4701, 4702, 4703 and 4704may be “staggered” to different positions on each layer, therebyminimizing the thickness of any single tab that must be cut. Inaddition, these connecting tabs 4710 may be solid or perforated asdesired. Additional connecting tabs 4712 are used to connect the framesidewalls 4706 of each layer to an exterior frame 4714.

After PCM machining, the four layers 4701, 4702, 4703 and 4704 arestacked and joined to one another as described above. The finished frameassembly 4700 may then hermetically joined to a single window sheetand/or to a substrate as previously described to create a multiple-unitcover assembly or a multiple-unit wafer-level package assembly. Thecompleted multiple-unit assembly is later singulated by cutting throughthe window sheet, connecting tabs and substrate (if applicable) betweenthe individual frame units 4705 to form a plurality of discrete units.Alternatively, rather than bonding the finished frame assembly 4700 to asingle window sheet, a plurality of smaller individual window sheets maybe placed on top of each individual frame unit 4705 (i.e., one windowsheet per frame unit), held in position with appropriate tooling, andhermetically bonded en masse. This eliminates the need to cut throughthe window sheets during singulation after bonding. In a similar manner,instead of bonding the finished frame assembly 4700 to a singlesubstrate, a plurality of smaller individual substrates (i.e., onesubstrate per frame unit 4705) may be hermetically bonded to the frameassembly 4700 en masse. While these fabrication methods may be used, itwill be understood that many of the other fabrication methods andtooling apparatus previously disclosed herein in connection with thehermetic bonding of window assemblies and wafer-level packages may alsobe applied to PCM frame assemblies.

Referring now to FIG. 49, shown is a perspective view of a multiple-unitassembly 4900 of PCM-fabricated frames suitable forresistance-seamwelding. It will be noted that the individual frames 4902are of flanged design, using a flange profile for the bottom PCM layer4904 and unflanged profile for upper PCM layer(s) 4906. As previouslydescribed, temporary connecting tabs 4908 hold together the individualframe units 4902 for easier material handing and simpler toolingrequirements during the process of joining the frame assembly to asingle large window sheet, or to multiple smaller window sheets (i.e.,one per frame unit 4902).

In yet another application of this discovery, transparent windowpanescan be hermetically joined to opposite sides of metallic or non-metallicspacers to create hermetically sealed multi-pane thermally insulatedwindow assemblies for residential and commercial buildings, forhousehold appliances and industrial equipment, and for aircraft andother vehicle windows. As in conventional insulated windows, the spacermaintains a gap between adjacent pairs of windowpanes. The space withinthis gap (i.e., the “gap cavity”) may contain a gas, such as air,nitrogen or argon, or may be a partial vacuum. The contents of the gapcavity reduce the flow of heat through the window, thereby providingthermal insulation. However, conventional insulated windows use eithernon-hermetic mechanical means (e.g., clamping, gaskets) or non-hermeticadhesives, such as rubber, glues, epoxies and resins, to mount thewindowpanes to the spacer. As a result, conventional insulated windowsare well known for developing leaks between the gap cavity and theoutside environment as they age. In contrast, true hermetically sealedmulti-pane insulated window assemblies can maintain their gas-tightintegrity indefinitely.

Referring now to FIGS. 50 and 51, there is illustrated the basichermetically sealed multi-pane window assembly, namely, a hermeticallysealed double-pane window assembly 5000. It will be understood that therelative dimensions of the assembly 5000 have been exaggerated forpurposes of illustration. The hermetic window assembly 5000 includes atransparent upper windowpane 5002, a transparent lower windowpane 5004,and a spacer 5006 having a continuous sidewall 5008 that defines a gapcavity 5010 therewithin. The upper windowpane 5002 and spacer 5006 arestacked on the lower windowpane 5004 (as indicated by the arrows in FIG.50) and then joined or bonded to form a hermetic seal between eachwindowpane and the spacer. If a particular gas mixture, pressure orother condition is desired for the gap cavity 5010, it may be introducedprior to, or during the bonding phase of assembly. After bonding, thegap cavity 5010 is hermetically sealed against any transfer of gas to orfrom the environment. The completed assembly 5000 (FIG. 51) can be used“as is,” or incorporated into higher level assemblies as describedbelow.

In some instances, it is desirable or necessary to introduce the desiredgas or partial vacuum into the gap cavity 5010 between the windowpanes5002 and 5004 after the bonding of the windowpanes to the spacer 5006.To do this, a passage may be formed through the wall 5008 of the spacer5006 and provided with a valve or pinch-off tube on the outside of thespacer. This may be done before or after bonding. Then, after bonding,the desired atmosphere (including a vacuum or partial vacuum) may beintroduced into the gap cavity 5010 through the valve or pinch-off tube.Obviously, if any undesirable gases are left in the gap cavity as a byproduct of the bonding process, the valve or pinch-off tube may be usedto first evacuate them from the gap cavity, and then to introduce thedesired gas or atmosphere. Once the gap cavity atmosphere is as desired,the valve or pinch-off tube may be sealed, e.g., by soldering or weldingit closed, to preserve the desired long-term hermeticity of the windowassembly.

The mating surfaces (i.e., the “seal ring areas”) of the windowpanes5002, 5004 and/or of the spacer 5006 may require various preparation orfinishing operations prior to the joining operation. Suitablepreparations and finishing operations are described herein in detail inconnection with window assemblies and wafer-level packages, andtherefore will not be repeated. It will however, be understood that suchpreparation and finishing operations may be applicable to thefabrication of hermetically sealed multi-pane window assemblies.

The windowpanes 5002 and 5004 of the hermetic window assembly 5000 willtypically be formed of glass, however, other transparent materials mayalso be used. For example, quartz, silicon, sapphire and othertransparent minerals may be used. In certain radiological applications,certain metals, metal alloys and ceramics are considered “transparent”(e.g., to X-rays), so in such applications these materials may also beused for windowpanes 5002 and 5004. Transparent plastics such aspolycarbonate may also be used, however, these materials may allowdiffusion of gas through the windowpane itself (as opposed to throughthe hermetic bond with the spacer) such that a true “hermeticallysealed” assembly cannot be maintained indefinitely.

Further, while the windowpanes 5002 and 5004 of the hermetic windowassembly 5000 will typically be flat in profile (i.e., viewed from theside) and rectangular in shape (i.e., viewed perpendicular to thesheet), this is not required. The windowpanes 5002 and 5004 may beconcave, convex or otherwise curved in profile, and each of thewindowpanes may have a different profile, as long as each windowpanemates with the spacer 5006 continuously around its entire upper or lower(as the case may be) periphery. In other words, during the bondingprocess, the respective surfaces of the windowpanes 5002 and 5004 mustbe in intimate contact with the respective surface of the spacer 5006 towhich they are being joined. Similarly, the windowpanes 5002 and 5004may have any shape, including circular, oval and triangular, providing acorrespondingly-shaped spacer 5006 is used.

It is envisioned that the spacer 5006 of the hermetic window assembly5000 will typically be a metal or metal alloy stamping, extrusion,casting or other part fabricated and joined together (if necessary) tocontinuously surround the gap cavity (it being understood that thespacer itself must hermetically withstand gas diffusion through it toand from the gap cavity). For large window assemblies, especially wherecost is a significant consideration, aluminum or aluminum alloys may beused for the spacer 5006. However, the use of metals or metal alloys forthe spacer 5006 is not required, and in some applications, may not evenbe preferred. Other materials believed suitable for forming the spacer5006, include, but are not limited to, glasses, ceramics, compositematerials, woven materials encapsulated in composite materials, andmaterials comprising a combination the materials listed above (includingmetals and metal alloys). In addition, some or all of the surfaces ofthe spacer 5006 may be coated or plated to promote bonding to thewindowpanes. Suitable coatings are believed to include, but are notlimited to glasses, metals, metal alloys, ceramics, composite materials,and woven materials encapsulated in a composite material.

It is currently believed that the preferred process for hermeticallyjoining the transparent windowpanes 5002 and 5004 to the spacer 5006 isdiffusion bonding. As previously described, diffusion bonding is aprocess by which a joint can be made between similar or dissimilarmetals, alloys, and/or nonmetals by causing the diffusion of atomsacross the surface interface. This diffusion is brought about by theapplication of pressure and heat to the surface interface for aspecified length of time. The bonding variables, e.g., temperature, load(i.e., pressure) and time, vary according to the kinds of materials tobe joined, the surface finishes, and the expected service conditions.

As previously described, a very important characteristic of diffusionbonding is the high quality of the joints produced. Diffusion bonding isthe only process known to preserve the properties inherent in monolithicmaterials, both in metal-to-metal joints and in joints involvingnon-metals. With properly selected process variables, i.e., temperature,pressing load, and time, the material at the joint (and adjacentthereto) will have the same strength and plasticity as the bulk of theparent material(s). When the process is conducted in vacuum, the matingsurfaces are not only protected against further contamination, such asoxidation, but may be cleaned, because the oxides present dissociate,sublime, or dissolve and diffuse into the bulk of the material. A gooddiffusion bond (sometimes known as a “diffusion weld”) is free fromincomplete bonding, oxide inclusions, cold and hot cracks, voids,warpage, loss of alloying elements, etc. If the interfacing surfaces arebrought into truly intimate contact, then there is no need for fluxes,electrodes, solders, filler materials, etc. Diffusion-bonded partstypically retain the original values of ultimate tensile strength, angleof bend, impact toughness, vacuum tightness, etc.

It is envisioned that in some instances, the bonding process for joiningwindowpanes 5002 and 5004 to the spacer 5006 will be done in vacuum orpartial vacuum (i.e., an evacuated chamber), in partial vacuum with theaddition of one or more gases to increase or accelerate reduction ofoxides (such as, but not limited to hydrogen), or in partial vacuum withthe addition of one or more inert gases such as argon. In otherinstances, the bonding process will be done in a special atmosphere toincrease oxidation of the frame material and/or the glass. This specialatmosphere could be a negative pressure, ambient pressure or positivepressure, with one or more gasses added to promote (instead of reduce)the oxidation of the frame material and/or the glass. The added gassesfor promoting oxidation include, but are not limited to oxygen.

In some instances, it is envisioned that the joint between thewindowpanes 5002 and 5004 and the spacer 5006 may include a chemicalbond between the spacer material and the windowpane material. Thischemical bond may be in addition to a true diffusion bond (i.e., atomicdiffusion). In other instances, the chemical bond may be present withlittle or no evidence of atomic diffusion.

For some combinations of materials, surface finishes and processconditions, the diffusion bonding process between windowpanes andspacers in hermetically sealed multi-pane window assemblies may befacilitated by the use of intermediate layers (also known as“interlayers”) of a dissimilar material placed between the windowpanesand the spacer during the diffusion bonding process. The interlayers arebelieved to act as one or more of the follows: as activators for themating surfaces; as high ductility interfaces between two less-ductilebase materials; as compensators for the stresses arising when a jointinvolves materials differing in thermal expansion characteristics; asaccelerators for mass transfer and/or chemical reactions; as buffers toprevent the formation of undesirable phases in the joint. As previouslydescribed, the interlayers may comprise metals, metal alloys, glassmaterials, solder-glass materials, solder-glass in tape form,solder-glass in sheet form, solder-glass in paste form, paste applied bydispensing or by screen-printing onto either the windowpane or spacer,solder-glass in powder form, glass powder mixed with water, alcohol oranother solvent and sprayed, brushed or otherwise applied onto eitherthe interface area of the spacer or the interface area of thewindowpane, ceramics, composite materials, woven materials encapsulatedin a composite material, or a material composed of a combination ofglass and metals and/or metal alloys.

After bonding, completed hermetically sealed multi-pane windowassemblies may be used in almost all applications where conventionalinsulated glass windows are used. However, unlike conventional windows,the hermetically sealed window assemblies will not lose their gas-tightintegrity. This makes the hermetically sealed window assemblies suitablefor premium installations in residential and commercial buildings (e.g.,to reduce warranty claims due to fogging or condensation between thepanes), in appliances such as ovens, or for use in severe or hazardousenvironments (e.g., in chemical plants, nuclear plants, outer space,etc.).

Referring now to FIGS. 52 and 53, there is illustrated a double-hungwindow unit equipped with a pair of hermetically sealed double-panewindow assemblies similar to those shown in FIGS. 50 and 51. Thedouble-hung unit 5200 includes upper and lower window frames 5202 and5204, respectively, which are slidingly mounted within a frame/railassembly 5206. A hermetically sealed double-pane window assembly 5000 ismounted in each window frame 5202 and 5204. The complete double-hungwindow unit 5200 (FIG. 53) can be installed into the rough-in frame of abuilding (not shown) as is a conventional window unit. It will beappreciated that the double-hung window unit is just one example, ashermetically sealed multi-pane window assemblies may also be used for,but not limited to, fixed frame windows, entry door windows, slidingglass doors, casement window assemblies and many other building andconstruction products.

Referring now to FIGS. 54 and 55, there is illustrated anotherhermetically sealed multi-pane window assembly, namely, a hermeticallysealed triple-pane window assembly 5400. It will be understood that therelative dimensions of the assembly 5400 have been exaggerated forpurposes of illustration. Similar to the double-pane assembly 5000previously described, the triple-pane assembly 5400 includes transparentwindowpanes 5402 and spacers 5406 having a continuous sidewall 5408 thatdefines a gap cavity 5410 therewithin. In this embodiment, however,there are three windowpanes 5402 interleaved with two spacers 5406. Alsoin this embodiment, the spacers 5406 are provided with pinch-off tubes5407 connected to passages 5409 through the spacer wall. As previouslydescribed, the pinch-off tubes will allow the atmosphere of the gapcavity 5410 to be adjusted after bonding. The upper windowpanes 5402 andthe spacers 5406 are stacked on the lower windowpane 5402 (as indicatedby the arrows in FIG. 54). The stack is then joined as previouslydescribed to form a hermetic seal between each windowpane and thespacer. It will be appreciated that the methods and principles offabrication for hermetically sealed two- and three-pane windowassemblies disclosed herein may be easily extended to allow thefabrication of hermetically sealed window assemblies having 4, 5, 6 . .. n windowpanes interleaved with 3, 4, 5 . . . (n−1) spacers,respectively.

Referring now to FIG. 56, there is illustrated one apparatus forfixturing multiple sets of window components for simultaneous diffusionbonding, thereby producing multiple hermetically sealed multi-paneinsulated window assemblies simultaneously. The fixture apparatus 5600includes a base 5601 upon which are stacked three sets of windowpanes5602 and spacers 5606 similar to those described in FIGS. 50-51. Ahydraulic or pneumatic ram 5608 supplies the pressure (i.e., load)against the top of the stack to press the windowpane and spacer elementstogether (against the base) during bonding. Separating the adjacentwindowpanes (i.e., those belonging to different assemblies) are dividers5610 formed of a material that will not bond to the windowpanes 5602,base 5601 or ram 5608 under the expected bonding conditions. The entirefixture apparatus is disposed inside a diffusion bonding chamber (notshown). The diffusion bonding chamber heats the fixture 5600 and itsstacked components to bonding temperature, and causes the ram 5608 toapply bonding load (pressure) to the stacked components. The bondingtemperature and pressure are maintained for the required bonding timenecessary to produce a complete hermetic seal between all of thewindowpanes 5602 and their respective spacers 5606. During the bondingprocess, the diffusion bonding chamber may be evacuated, pressurized,and/or filled with one or more gases as necessary to be sure the gapcavities of the assemblies have the desired contents, and/or to promotethe bonding of the components. After bonding, the three hermeticallysealed double-pane insulated window assemblies are complete. Of course,if the assemblies are equipped with valves or pinch-off tubes throughthe spacers as previously described, then the atmospheres of the gapcavities may still be adjusted as desired before the assemblies arefinally hermetically sealed. It will be appreciated that similarapparatus and processes can be use to simultaneously produce largenumbers of hermetically sealed multi-pane insulated window assemblies.

While diffusion bonding is believed to be the preferred method forjoining the windowpanes to the sheets in a hermetically sealedmulti-pane window assembly, another bonding apparatus, known as a HotIsostatic Press (“HIP”) may be used in lieu of the conventionaldiffusion bonding chamber with internal ram illustrated in FIG. 56. AHot Isostatic Pressing (HIP) unit provides the simultaneous applicationof heat and high pressure. In the HIP unit a high temperature furnace isenclosed in a pressure vessel. Work pieces (e.g., the window assemblycomponents) are heated and an inert gas, generally argon, appliesuniform pressure. The temperature, pressure and process time are allcontrolled to achieve the optimum material properties.

Further, while diffusion bonding is believed preferred, manywindow-to-frame joining/bonding methods may be used to join thewindowpanes to the sheets in a hermetically sealed multi-pane windowassembly. These other methods include, but are not limited to,soldering, brazing, welding, electrical resistance heating (ERH), theuse of metallization, solder preforms, etc. A large number of suitablemethods are described herein in detail in connection with hermeticwindow assemblies and wafer-level packages, and therefore will not berepeated. It will however, be understood that such window-to-framejoining/bonding processes may be applicable to the fabrication ofhermetically sealed multi-pane window assemblies.

Preferably, when fabricating hermetically sealed multi-pane insulatedwindow assemblies, the coefficient of (linear) thermal expansion (CTE)of the spacer material(s) is matched as well as possible to the CTE ofthe associated glass windowpanes. The CTE of most glasses is fairlyconstant from approximately 273° K (0° Centigrade) up to the softeningtemperature of the glass. However, some metals and alloys have verydifferent CTEs at different temperatures. Therefore, the average CTE ofthe spacer material(s) at the elevated glass-to-spacer bondingtemperature should be matched as closely as possible to the average CTEof the glass over the same temperature range. The closer the averageCTEs of the two materials, the lower will be the residual stresses inthe spacer and the glass windowpanes after the assembly cools from theelevated bonding temperature back to ambient (room temperature).

The long-term reliability of the spacer-to-glass seal is affected by thedegree of matching of the CTEs of the spacer material and the glass forthe anticipated end-use environment. For example, if the window assemblyis expected to be exposed to temperatures from −40° C. to 100° C. (−40°F. to 212° F.), then the spacer material and the glass material shouldhave closely matched CTEs over this temperature range. If CTE of thespacer material cannot be exactly matched to the CTE of the glassmaterial, then it is desirable that the CTE of the spacer materialshould be slightly greater than that of the glass. In such case (i.e.,where the CTE of the spacer material exceeds that of the glass), thespacer would contract more than the glass during cool-down from theelevated bonding temperature back to ambient, resulting in the glassbeing in slight compression. This is preferable to the glass being intension, since glass in tension is prone to cracking.

It is thus desirable when designing and fabricating hermetically sealedmulti-pane insulated window assemblies to take into consideration dataon the ranges of the coefficient of linear thermal expansion (CTE) ofmetals, metal of alloys and other spacer materials, along with data onthe CTE values of glasses and other windowpane materials, so as toensure the minimum post-bonding stresses, the maximum long-termreliability of the spacer-to-glass seals, and prevention of cracking ofthe glass windowpanes.

This disclosure further describes the attachment of two or moretransparent windowpanes to a metallic or non-metallic spacer in order tocreate hermetic, thermally insulated window assemblies for residentialand commercial building construction and other applications. The spacermaintains a gap or space between the pairs of windowpanes. This spacemay contain a gas, such as nitrogen or argon, or may be a partial orhigh vacuum.

A Vacuum Glazing Unit (VGU) is an Insulating Glass (IG) window unit thatcontains and maintains a partial vacuum inside the Insulating Glass Unit(IGU). A total vacuum would be the complete absence of any atoms ormolecules inside the confined space. A total vacuum is today notpractical to produce, so the term “partial vacuum” is used to denote anachievable level of vacuum or significantly reduced amount of atoms andmolecules with a defined volume of space.

A vacuum-glazing unit (VGU) is a window assembly consisting of, at aminimum, two windowpanes with a space between them and a sealed frameassembly that is joined to the windowpanes and which, together with thewindowpanes, defines, contains and maintains a volume of space thatholds a practical level of vacuum. The purpose of this type ofconstruction is to produce an IG window unit with the potential for ahigher level of thermal insulation that can be obtained my most otherconstructions of IG units (IGUs). The VGU's higher level of thermalinsulating capability when compared to gas-filled IGUs results from thesubstitution of the partial vacuum for the fill gas, since a vacuum isknown to be the ultimate thermal insulator. Its ultimate insulatingvalue comes from the absence or very low amount of atoms and/ormolecules, therefore having very few substances in the volume of thevacuum to mechanically conduct or transfer thermal energy.

To make a VGU reliable and practical for installations in theoutside-facing (exterior) walls and doors of buildings, the VGU must beable to withstand changes in temperature and barometric pressure, anddifferences in the building's inside and outside temperature andbarometric pressure. Important factors for long-term insulatingperformance, reliability and durability of the VGU include the level ofhermeticity of the components and assembled VGU, the strength andintegrity of the hermetic attachment of the components forming theoverall structure of the VGU, and maintaining a practical separation ofthe VGU's inside-facing and outside-facing windowpanes. Inside-facingrefers to the side of the VGU that faces and is exposed to the inside(interior) of the building structure and outside facing refers to theside of the VGU that faces and is exposed to the outside (exterior) ofthe building structure.

Referring now to FIG. 57, there is illustrated a conventionaldouble-pane VGU in accordance with the prior art for purposes ofexplaining the vocabulary commonly used in the building window industryfor the windowpanes of a double-pane VGU, and which will sometimes beused herein. The VGU 5750 includes inner and outer window panes (alsocalled “panes” or “lites”) 5752 and 5754, respectively. In the industry,the outside pane 5754 is sometimes referred to as window #1 and theinside pane 5754 is sometimes referred to as window #2. A frame 5756mounts the VGU in the building's inner and outer walls 5758 and 5760,respectively, and also maintains separation between the panes 5752 and5754 to form an insulating gap (also called a “cavity”) 5762. In theindustry, the outside-facing surface of the outside windowpane 5754 issometimes referred to as surface° #1, the inside-facing surface of theoutside windowpane is sometimes referred to as surface° #2, theoutside-facing surface of the inside windowpane 5752 is sometimesreferred to as surface° #3, and the inside-facing surface of the insidewindowpane is sometimes referred to as surface° #4.

The rate of expansion and contraction of a material per degree change intemperature is called the coefficient of thermal expansion (CTE) orthermal coefficient of expansion (TCE). CTE and TCE are typicallyexpressed as Parts-Per-Million change in dimension per Degree Centigradeor Degree Fahrenheit change in temperature, or abbreviated as PPM/° C.or PPM/° F.

In general, the exterior of most buildings will see larger changes intemperature than the interior of the buildings due to daily outsideweather changes. Because of this, the outside-facing surface of the VGU(surface #1) will be exposed to greater changes in temperature than theinside-facing surface (surface #4). If both the inside and outsidefacing windowpane have the same average CTE, the difference intemperature between them will cause the outside-facing windowpane toexpand and contract more than the inside-facing windowpane. Any frame orseal mechanism holding the VGU together will have to compensate for therelative dimensional positions of the inside-facing and outside facingwindowpanes. If the frame or seal mechanism is not compliant, that is,if it cannot compensate for the difference in location between theperimeters of the two windowpanes, then the bond attaching the frame orseal mechanism to the two windowpanes will incur stresses as a result ofthe effect of the relative changes in temperature between theinside-facing and outside-facing surfaces of the VGU. It is for thisreason that the frame mechanism must be designed and constructed withspecial features. These features include having the frame member's CTEclosely matched or similar to the windowpane or other item(s) to whichit will be attached, and to be compliant in its design and use ductilematerials in its construction. By incorporating these attributes, theframe member will be capable of expanding and contracting and thusacting like a spring to compensate for the difference in locations thatthe items to which the frame member is attached are trying to occupy.

Another attribute the frame member of the VGU should have is to beconstructed of relatively low thermal conductivity material(s). This isbecause the frame member will conduct heat from the hotter surface it isattached (bonded, joined) onto, to the cooler surface onto which it hasbeen attached (bonded, joined). Thus minimizing the thermal conductivityof this frame member minimizes the conduction of heat from onewindowpane to the other windowpane of the VGU.

The preferred method of hermetically attaching the frame members to thewindowpanes is by a process called diffusion bonding, a solid-statejoining process. This process is also known as thermal-compressionbonding (TC bonding). Diffusion bonding is a process by which a jointcan be made between similar and dissimilar metals, alloys, andnonmetals, through the action of diffusion of atoms across theinterface, brought about by the bonding pressure and heat applied for aspecified length of time. The bonding variables (temperature, load andtime) vary according to the kind of materials to be joined, surfacefinish, and the expected service conditions.

A very important distinction of diffusion bonding is the high quality ofjoints. It is the only process known to preserve the properties inherentin monolithic materials, in both metal-to-metal and nonmetal joints.With properly selected process variables (temperature, pressing load,and time), the material at and adjacent to the joint will have the samestrength and plasticity as the bulk of the parent material(s). When theprocess is conducted in vacuum, the mating surfaces are not onlyprotected against further contamination, such as oxidation, but arecleaned, because the oxides present dissociate, sublime, or dissolve anddiffuse into the bulk of the material. A diffusion bonded joint is freefrom incomplete bonding, oxide inclusions, cold and hot cracks, voids,warpage, loss of alloying elements, etc. Since the edges are brought inintimate contact, there is no need for fluxes, electrodes, solders,filler materials, etc. Diffusion-bonded parts usually retain theoriginal values of ultimate tensile strength, angle of bend, impacttoughness, vacuum tightness, etc.

The bonding process for joining glass and other transparent andsemi-transparent materials to a frame material may be done in vacuum orpartial vacuum (an evacuated chamber), vacuum with the addition of oneor more gases to increase or accelerate reduction of oxides (such as,but not limited to hydrogen), and vacuum with the addition of one ormore inert gases such as argon.

The bonding process for joining glass to a frame material may be done ina special atmosphere to increase oxidation of the frame material and/orthe glass. This special atmosphere could be a negative pressure, ambientpressure or positive pressure, with one or more gasses added to promote(instead of reduce) the oxidation of the frame material and/or theglass. The added gasses for promoting oxidation include, but are notlimited to oxygen.

In some instances, the bond (joint) resulting from the bonding processwill exhibit a chemical bond between the frame/spacer material and theglass. This chemical bond may be in addition to evidence of a diffusionbond (atomic diffusion). In other instances, the bond (joint) willexhibit little or no evidence of atomic diffusion.

Composition of the frame members joined to the windowpanes and/or to theinternal spacer assembly. The frame members are hermetic structurescomposed of one or more materials. These materials include, but are notlimited to: a glass material; a metal material; a metal alloy material;a ceramic material; composite materials; woven materials encapsulated ina composite material; and a material composed of a combination of two ormore of the items listed above.

The frame members may be coated or plated to promote bonding(hermetically attaching) two or more frame materials to each other.These materials include, but are not limited to: a glass material; ametal material; a metal alloy material; ceramics; and compositematerials.

The frame members may be coated or plated to promote bonding to theglass windowpane. These materials include, but are not limited to: aglass material; a metal material; a metal alloy material; a ceramicmaterial; composite materials; woven materials encapsulated in acomposite material; and a material composed of a combination of two ormore of the items listed above.

A typical diffusion bonding process involves holding surface-preparedcomponents together under load (i.e., bonding pressure) at an elevatedtemperature for a specified length of time. The specific values of thediffusion bonding parameters (i.e., pressure, temperature and time) mayvary according to the kind of materials to be joined, their surfacefinish, and the expected service conditions. Generally speaking,however, the bonding pressures used are typically below those that willcause macrodeformation of the parent materials, and the temperature usedis typically less than 80% of the parent material's melting temperature(in ° K). As previously described, in many cases, diffusion bonding isperformed in a protective atmosphere or vacuum, however, this is notalways required.

Assembly of a VGU with the use of intermediate layers (interlayers) isnow described in further detail. The glass-to-frame seal may be madeusing one or more intermediate layers between the window and the frameassembly during the diffusion bonding process. These intermediate layersare hereafter referred to as interlayers. The interlayers may serve oneor more of the following features: as activators for the matingsurfaces; sometimes the interlayer material has a higher ductility incomparison to the base materials; as compensators for the stressesarising when a seal involves materials differing in thermal expansion;as accelerators for mass transfer and/or chemical reactions; as buffersto prevent the formation of undesirable phases; or other purposes notmentioned here. The interlayers may comprise: a glass material; asolder-glass material; solder-glass in tape form; solder-glass in sheetform; solder-glass in paste form (e.g., paste would be applied bydispensing or by screen-printing onto either the window component or theframe component); solder-glass in powder form (e.g., the glass powderwould be mixed with water, or alcohol or another solvent and sprayed orbrushed (painted) onto either the sealing area of the frame or thesealing area of the windowpane); a metal material; a metal alloymaterial; a material other than glass, glass-solder, metal or metalalloy, including, but not limited to: ceramics; composite materials;woven materials encapsulated in a composite material; or a materialcomprising a combination of glass and metals and/or metal alloys.

It is important to distinguish the use of diffusion bonding interlayersfrom the use of conventional solder alloys (in perform, paste and otherforms) or solder glass (in perform, paste and other forms) and otherprocesses. For purposes of this application, an interlayer is a materialused between mating surfaces to promote the diffusion bonding of thesurfaces by allowing the respective mating surfaces to diffusion bond tothe interlayer or directly to one another. For example, with the properinterlayer material, the diffusion bonding temperature for the jointframe member and the interlayer material, and for the joint between theinterlayer material and the windowpane, may be substantially below thediffusion bonding temperature of a joint formed directly between theframe member material and the windowpane material. Thus, use of theinterlayer allows diffusion bonding together of the two or threeassembly component layers at a temperature that is substantially belowthe diffusion bonding temperature that would be necessary for bondingthose two or three component layer materials directly. The joint, whichwill preferably be hermetic, is still formed by the diffusion bondingprocess, i.e., none of the parent materials involved melts during thebonding process and the material of the interlayer diffuses atomicallyinto the parent material. This distinguishes diffusion bonding usinginterlayers from other processes such as the use of solder alloy (in avariety of forms) or solder glass performs or paste, in which the soldermaterial forms only a surface bond between the materials being joined.It is possible to use materials conventionally used for solders, forexample, as interlayers for diffusion bonding. However, when used asinterlayers they are used for their diffusion bonding properties and notas conventional solders.

The use of interlayers in the production of VGUs or other devices mayprovide additional advantages over and above their use as promotingdiffusion bonding. These advantages include interlayers that serve asactivators for the mating surfaces. Sometimes the interlayer materialswill have a higher ductility in comparison to the base materials. Theinterlayers may also compensate for stresses that arise when the sealinvolves materials having different coefficients of thermal expansion orother thermal expansion properties. The interlayers may also acceleratethe mass transfer or chemical reaction between the layers. Finally, theinterlayers may serve as buffers to prevent the formation of undesirablechemical or metallic phases in the joint between components.

In some embodiments, a variation of diffusion bonding known as LiquidPhase diffusion bonding or sometimes, Transient Liquid Phase diffusionbonding (i.e., “TLP diffusion bonding”) may be used for some or all ofthe bonds required in the bonded assemblies. In TLP diffusion bonding,solid state diffusional processes caused by the elevated pressure (i.e.,load) and heat of the bonding process lead to a change in materialcomposition (e.g., a new material phase) at the bond interface, and theinitial bonding temperature is selected as the temperature at which thisnew phase melts. Alternatively, an interlayer of a material having alower melting temperature than the parent material may be placed betweenthe layers to be joined, and the initial bonding temperature is selectedas the temperature at which the interlayer melts. Thus, a thin layer ofliquid spreads along the interface to form a transient joint at a lowertemperature than the melting point of either of the parent materials.The initial bonding temperature is then reduced slightly to a secondarytemperature allowing solidification of the melt. This elevatedtemperature (i.e., the secondary temperature) and the elevated pressure(i.e., load) are maintained until the now-solidified transient jointmaterial diffuses into the parent materials by solid-state diffusion,thereby forming a diffusion bond at the junction between the parentmaterials.

Sometimes the interlayer will not be a separate item from the two itemsto be joined, but rather be a material that has been applied to one orboth of the surfaces of the to-be-mated surfaces of the items to bejoined together. When the interlayer is pre-applied to one or bothmating surfaced, the interlayer may be pre-applied by one of a varietyof methods including, but not limited to spray deposition, vapordeposition, plating including solution bath plating, growing theinterlayer material onto the to-be-mated item's surface, painting bybrush or roller, and by many other means.

It will be appreciated that the terms “diffusion bonding” and “thermalcompression bonding” (and its abbreviation “TC bonding”) are often usedinterchangeably throughout this application and in the art.Metallurgists prefer the term “diffusion bonding”, while the term“thermal compression bonding” is preferred in many industries (e.g.,semiconductor manufacturing) to avoid possible confusion with othertypes of “diffusion” processes used in semiconductor manufacturing.Regardless of which term is used, as previously discussed, diffusionbonding refers to the family of bonding methods using heat, pressure,atmospheres and time alone to create a bond between mating surfaces at atemperature below the normal fusing temperature of either matingsurface. In other words, neither mating surface is intentionally melted,and no chemical adhesives are used.

The design and materials used for VGUs (and IGUs) can vary. Somevariations are shown in FIGS. 58 a though 96 c. For purposes ofdescribing these figures, “upper” and “lower” are used to describe therelative position of the components of the VGU instead of “inside”,“inside facing”, “indoor”, “outside”, “outside facing”, “outdoor”, etc.Furthermore, the VGUs are shown illustrated in a horizontal viewalthough they would be installed vertically in most situations, such aswhen installed in vertical walls and doors. Horizontal installationscould include when the VGU is part of a skylight unit on a flat,horizontal portion of a ceiling or floor. It should be further notedthat although the descriptions for the items and details in the figuresuse the terms “upper”, “lower”, “top” and “bottom” to describe thepositional relationship of the items and details, the relativerelationships of many items could often be reversed, such that the“upper” and “lower” items could be interchanged. Thus, the figures arenot intended to imply which side of the VGU would face outdoors andwhich side would face indoors, or towards a particular direction onceinstalled into the VGU's next higher assembly.

FIGS. 58 a and 58 b illustrate the basic concept and components of avacuum glazing unit (VGU). The VGU 5800 comprises an upper frame member5810, bonded to the top surface 5831 of an upper windowpane 5830. Alower frame member 5890 is bonded to the bottom surface 5873 of thelower windowpane 5870. Spacers/stand-offs 5840 are applied to the topsurface 5871 of the lower windowpane 5870. These spacers are for thepurpose of keeping the upper windowpane 5830 from coming in contact withthe lower windowpane 5870.

The frame member 5810 is shown in a side view, cross section form. Inits vertical form, it contains at least two radii, shown as upper,inside radius 5815 and lower, outside radius 5817. These radii providecompliancy to the frame member.

The spacers/stand-offs 5840 may be composed of a variety of materialsand may be applied to the windowpane surface by a variety of means.These spacers should preferably be made with (composed of) a low thermalconductivity material, since they form a path of thermal conductionbetween the adjacent surfaces of the two windowpanes. They should outgasvery little once included in the assembled and sealed VGU. They shouldbe small enough to not be noticeable under almost any circumstancesunless the observer is very close to the VGU. Their numbers anddistribution must be sufficient to maintain a mechanical separation ofthe windowpanes' surfaces 5833 and 5871 from one another under allintended VGU installations.

The spacers/stand-offs 5840 may be applied to the surface 5871 of thewindowpane 5870 by methods including, but not limited to ink jetdispensing, stencil printing or screen printing, automatedpick-and-place equipment where an adhesive might be used to hold thespacers/stand-offs 5840 in place after attachment to the surface 5871and at least until the VGU is assembled and sealed, or by other means.If ink jet dispensing is used to create the spacers/stand-offs 5840,each spacers/stand-off may be formed by the application of more than onedrop of material. Multiple drops of jetted material could be used tomake the desired area of spacer surface 5843 on the windowpane's surface5871. Multiple drops of jetted material could be used to create thedesired height of the spacer 5840. In some embodiments, the spacer's topsurface 5841 is flat, while in other embodiments, the top surface 5841would be not be flat, but rather would have a radius (be rounded or domeshaped) to minimize the contact area between it and the windowpanesurface 5833.

Whenever a spacer is used to maintain separation of two windowpanes, thesurface of the windowpane may be treated or coated with a substance toreduce any friction that could result from the relative movement of thespacer to the windowpane as a result of changes in temperature causingchanges in the dimension, and thus relative location of the spacer(s) tothe windowpane's surface. Friction where the spacer(s) surface 5841moved relative to the windowpane's surface 5833 could result in physicaldamage (including causing scratches); and/or affect the opticalappearance of one or both items; and/or affect the transparency ofeither or both the spacer(s) and the windowpane. Coatings to reducefriction and/or to reduce or eliminate the possibility of any of thedamage described above include chemical vapor deposited diamond (CVDdiamond). Additionally, materials such as sheet films could be appliedto one or both surfaces (5833 and/or 5841).

Often, IG windows are coated on inside surfaces #2 and/or #3 withmaterials intended to enhance certain features of the IGU. These includelow-emissivity (low-e) coatings, and chromatic or chromeric coatingssuch as electrochromic and polychromic coatings. These and othercoatings in use today could also be applied to the inside surfaces #2and/or #3 of the VGUs described herein.

Some IGUs are now offered with special coatings applied to the outsidesurfaces #1 and/or #4. These coatings provide features and functionsincluding making the windows easier to clean. The VGUs described hereincould also have windows with these and other coatings applied to outerfacing surfaces #1 and #4.

Regardless of whether any coatings are applied to surfaces #1, #2, #3 or#4, if the coatings can withstand the diffusion bonding temperature(s)used to attach the frame member to the windowpane, then the coating maybe applied to the windowpane prior to the diffusion bonding process.Should the coating(s) not be able to withstand the diffusion bondingtemperature(s) used to attach the frame member to the windowpane, thenthe coating(s) would have to be applied to the surface(s) of thewindowpane after performing the diffusion bonding process. The samewould be applicable for any films applied to any surface of eitherwindowpane.

Before bonding the frame member and the windowpane together, with orwithout the use of an interlayer, it may be necessary to remove anypre-applied coatings on the windowpane's surface where the two itemswill be joined. Coating removal methods could include chemical removal,mechanical abrasion including sanding or grinding, and/or laserablation.

During the actual diffusion bonding process, the upper bonding surfaces5811 of upper frame member 5810 are positioned against the top surface5831 of the upper windowpane 5830. The bonding surfaces 5811 and thewindowpane 5830 are pressed together with sufficient force to produce apredetermined contact pressure between the bonding surfaces and thewindowpane along a first junction region, and the junction regions isheated to produce a predetermined temperature along the first junctionregion. The previous two steps may be conducted simultaneously or ineither order, and further may be conducted in a vacuum or specialatmosphere. The predetermined contact pressure and the elevatedtemperature are maintained until a diffusion bond is formed between theupper frame member 5810 and the upper windowpane 5830 around theperiphery of the windowpane.

Similarly, the top bonding surfaces 5891 of lower frame member 5890 arepositioned against the bottom surface 5873 of the lower windowpane 5870.The bonding surfaces 5891 and the windowpane 5870 are pressed togetherwith sufficient force to produce a predetermined contact pressurebetween the bonding surfaces and the windowpane along a second junctionregion, and the junction regions is heated to produce a predeterminedtemperature along the second junction region. The previous two steps maybe conducted simultaneously or in either order, and further may beconducted in a vacuum or special atmosphere. The predetermined contactpressure and the elevated temperature are maintained until a diffusionbond is formed between the lower frame member 5890 and the lowerwindowpane 5870 around the periphery of the windowpane.

Returning now to FIGS. 58 a and 58 b, once the frame members areattached to windowpanes and the spacers are applied to the lowerwindowpane, the unit is ready for final assembly. This entails thehermetic bonding of the lower surface 5813 of the upper frame member5810, to the upper surface 5891 of the lower frame member 5893.

FIG. 58 c points out the top surface 5819 of the upper frame's bottomedge/flange/foot and the bottom surface 5893 of the lower frame member.Heat can be applied simultaneously to both surfaces 5819 and 5893 tofrom a hermetic bond or joint that joins the upper frame member to thelower frame member. Heat application methods include electricalresistance seam welding, can welding, and laser welding. Often anadditional material is pre-applied to one or both of the surfaces 5813on the bottom of the upper frame member 5810 and to surface 5891 on thetop of the lower frame member prior to bonding the two frame members toeach other. One such common material is nickel. When nickel ispre-applied to one or both materials, the joint region is heated to atemperature sufficiently high enough to melt the nickel coating, and theresulting joint is a nickel solder joint. A common method of applyingthe nickel to the frame member, when the frame is made of a metal ormetal alloy material, is to solution bath plate the nickel onto theframe member. Sometimes an additional, very thin metal or metal alloy issubsequently plated or otherwise applied on top or the nickel or othersolder material. This is usually done for cosmetic purposed or to helpprevent oxidation of the solder material prior to the soldering orbrazing process that joins the two frame members together.

FIG. 58 d shows the point of heat application to be at the junction ofcontact 5899 between the upper and lower frame members. Heat applicationmethods include laser and forced air convection.

FIG. 58 e shows the points of heat application to be at both thelocations of FIG. 58 c and FIG. 58 d. This can be accomplished by oneof, or a combination of heating methods, including laser, forced-airconvection, heater bars (such as is used for hot-bar soldering ofelectronics), and seam welding where the electrodes contact all threesurfaces.

In preferred embodiments, the frame members of the VGU are sealedtogether while in a vacuum environment, thereby “automatically” creatingthe desired vacuum within the gap, and eliminating the need for apinch-tube, valve, etc. for evacuation of the VGU gap after it isassembled and sealed. In other embodiments, however, a pinch-tube orvalve may be used, and the VGU gap may be evacuated after assembly.

While vacuum provides the best insulating properties for multi-paneinsulating window assemblies, the physical configuration of the VGUs ofthe current invention will also benefit multi-pane insulating windowassemblies that contain a fill gas or other insulating substances, e.g.,aerogels, between the windowpanes. Having a compliant frame assemblythat is also hermetically sealed is expected to extend the usefulinsulating life of these types (i.e., non-vacuum) of windows, too. Somefill gasses, like xenon, are more insulating than krypton, but currentlytoo expensive for most consumers. It is anticipated that when multi-paneinsulating window assemblies can be expected to hold an exotic fill gasfor 20-50 years, the alternative fill gases would become practical touse. On the other hand, non-gas insulating alternatives such as aerogelsmay or may not need hermetic encapsulation like vacuum and gas-filledwindows.

FIG. 58 f shows a perspective view of one embodiment of a compliantframe member suitable for use in a VGU or IGU such as those described inconnection with FIGS. 58 a-58 e. The frame 5808 is compliant in allthree axes in a side region 5811 below a top flange 5812 and a bottomflange 5814. The top flange 5812 is adapted for bonding to the topsurface of an upper windowpane (e.g., surface 5831 in FIG. 58 a), andthe bottom flange 5814 is adapted for bonding to the top surface of alower frame member (e.g., surface 5891 in FIG. 58 a). The side region5811 may incorporate combinations of compliant shapes to provide thenecessary multi-dimensional compliance. In the illustrated embodiment,the side region 5811 includes corrugations 5816, convex recurves 5818and concave recurves 5820, however, it will be understood that otherconfigurations are within the scope of the invention. The features ofthe frame member 5810 in FIGS. 58 a-58 e may correspond to the featuresof embodiment 5808 as follows: upper bonding surface 5811 (FIG. 58 a)may be the reverse side of upper flange 5812 (FIG. 58 f); upper radius5815 (FIG. 58 a) may be the reverse side of upper recurve 5818 (FIG. 58f); lower radius 5817 (FIG. 58 a) may be the lower recurve 5820 (FIG. 58f); and lower bonding surface 5813 (FIG. 58 a) may be the reverse sideof lower flange 5814 (FIG. 58 f).

FIGS. 59 a and 59 b show, respectively, an exploded view and anassembled view of a VGU in accordance with another embodiment. The VGU5900 is generally similar to the VGUs previously described herein,however, it comprises a woven spacer 5950 as further described below.The VGU 5900 further comprises an upper windowpane 5930 having a topsurface 5931 and bottom surface 5933, and a lower windowpane 5970 havinga top surface 5971 and a bottom surface 5973. The woven spacer 5950includes warp fibers 5953 comprising generally parallel strands of afirst fiber/filament interwoven with weft fibers 5955 comprisinggenerally parallel strands of a second fiber/filament running generallyperpendicular to the warp. The spacer maintains separation between theinner surfaces 5933 and 5971 of the windowpanes. The VGU 5900 is heldtogether by an upper frame member 5910 and a lower frame member 5990.The upper frame member 5910 has a top bonding surface 5911 for hermeticbonding to the top surface 5931 of upper windowpane 5930, an upperinside radius 5915, a lower outside radius 5917 and a bottom bondingsurface 5913. The lower frame member 5990 includes a top surface 5991for hermetic bonding to the lower bonding surface 5913 of the upperframe member 5910, and for hermetic bonding to the bottom surface 5973of the lower windowpane 5970.

One potential material for the warp fibers/filaments 5953 and weftfibers/filaments 5955 would be glass fiber such as is used for opticalfiber. This type of fiber has several benefits, including abundantsupply, availability in extremely small diameters, and a fair level ofoptical transparency. The points where the warp and weft fibers come incontact with each other are higher, taller, and thicker than thediameter of either the warp or weft fibers by themselves. It is theseoverlapping regions that provide the stand-offs that separate the upperwindowpane 5930 from the lower windowpane 5970. It should be appreciatedthat employing only parallel warps or wefts between the windowpanesurfaces 5933 and 5971 could maintain separation of the two windowpanes,but the surface contact area would be much greater that when using awoven spacer with the appropriate mesh spacing.

FIGS. 60 a and 60 b show, respectively, an exploded view and anassembled view of a VGU in accordance with another embodiment. The VGU6000 is generally similar to the VGUs previously described herein,however, it comprises one or more interlayers 6020, 6080 and/or 6086 tofacilitate diffusion bonding of the frame members and windowpanes. Thereasons for using an interlayer are further described herein.

The VGU 6000 comprises an upper windowpane 6030 having a top surface6031 and bottom surface 6033, and a lower windowpane 6070 having a topsurface 6071 and a bottom surface 6073. A plurality of spacers 6040,each having a upper surface 6041 and lower surface 6043 are disposedbetween the inner surfaces 6033 and 6071 of the windowpanes to maintaintheir separation. The VGU 6000 is held together by an upper frame member6010 and a lower frame member 6090. The upper frame member 6010 has atop bonding surface 6011 for hermetic bonding to the top surface 6031 ofupper windowpane 6030, an upper inside radius 6015, a lower outsideradius 6017 and a bottom bonding surface 6013. The lower frame member6090 includes a top surface 6091 for hermetic bonding to the lowerbonding surface 6013 of the upper frame member 6010, and for hermeticbonding to the bottom surface 6073 of the lower windowpane 6070. A firstinterlayer 6020 having upper surface 6021 and lower surface 6023 may beemployed for diffusion bonding purposes between bonding surfaces 6011and 6031 of the upper frame member 6010 and upper windowpane 6030,respectively. A second interlayer 6080 having upper surface 6081 andlower surface 6083 may be employed for diffusion bonding purposesbetween bonding regions 6073 and 6091 of the lower windowpane 6070 andlower frame member 6090, respectively. A third interlayer 6086 havingupper surface 6087 and lower surface 6089 may be employed for diffusionbonding purposes between bonding surfaces 6013 and 6091 of the upperframe member 6010 and lower frame member 6090, respectively. Use of theinterlayers is optional.

FIGS. 61 a and 61 b show, respectively, an exploded view and anassembled view of a VGU in accordance with another embodiment. The VGU6100 is generally similar to the VGUs previously described herein,however, it comprises a windowpane that was fabricated to includeintegral spacers/standoffs that will be used to maintain the separationof the two windowpanes. Having the windowpane produced with integratedspacers mitigates the need for applying individual spacers to one of thewindowpanes. The VGU 6100 comprises an upper windowpane 6130 having atop surface 6131 and bottom surface 6133, and a lower windowpane 6160having a top surface with integral stand-offs 6161 and a bottom surface6163. The integral stand-offs 6161 maintain the separation between thewindowpanes. The VGU 6100 is held together by an upper frame member 6110and a lower frame member 6190. The upper frame member 6110 has a topbonding surface 6111 for hermetic bonding to the top surface 6131 ofupper windowpane 6130, an upper inside radius 6115, a lower outsideradius 6117 and a bottom bonding surface 6113. The lower frame member6190 includes a top surface 6191 for hermetic bonding to the lowerbonding surface 6113 of the upper frame member 6110, and for hermeticbonding to the bottom surface 6163 of the lower windowpane 6160.Although FIGS. 61 a and 61 b show a VGU with spacers/stand-offsincorporated into the fabrication of the lower windowpane 6160, it willbe appreciated that stand-offs could be fabricated into the upperwindowpane, or into both windowpanes, in other embodiments.

FIGS. 62 a, 62 b, and 62 c illustrate embodiments of a windowpane,similar to the lower windowpane 6160 described in connection with FIGS.61 a and 61 b, having spacers on one of its surfaces that wereincorporated into the windowpane's fabrication. It will be appreciatedthat stand-offs are not necessarily drawn to scale, thus the proportionsand relative spacing of the stand-offs may be different from thatillustrated. Windowpane sheet 6260 comprises a substrate having asubstantially flat top side 6261 and bottom side 6263, and a pluralityof stand-off features 6265 extend upward from the top surface. In theillustrated embodiment, the stand-offs 6265 have a truncated conicalconfiguration and an evenly arrayed distribution, but in otherembodiments the stand-offs may have other configurations and/ordistributions.

FIGS. 63 a and 63 b show, respectively, an exploded view and anassembled view of a VGU in accordance with another embodiment. The VGU6300 is generally similar to the VGUs previously described herein,however, it comprises a transparent sheet center spacer unit 6350 thatis fabricated with spacers/stand-off's as part of the spacer sheet's topand bottom sides to enhance the thermal performance (i.e., insulatingproperties) of the VGU. The spacer sheet with integrated spacerseliminates the need for applying individual spacers to one of thewindowpanes.

The VGU 6300 comprises an upper windowpane 6330 having a top surface6331 and bottom surface 6333, and a lower windowpane 6370 having a topsurface 6371 and a bottom surface 6373. The spacer unit 6350 includesintegral stand-offs 6351 on the upper surface, and stand-offs 6353 onthe bottom surface. The spacer unit 6350 is placed between thewindowpanes 6330 and 6370 to maintain the separation between them. TheVGU 6300 is held together by an upper frame member 6310 and a lowerframe member 6390. The upper frame member 6310 has a top bonding surface6311 for hermetic bonding to the top surface 6331 of upper windowpane6330, an upper inside radius 6315, a lower outside radius 6317 and abottom bonding surface 6313. The lower frame member 6390 includes a topsurface 6391 for hermetic bonding to the lower bonding surface 6313 ofthe upper frame member 6310, and for hermetic bonding to the bottomsurface 6373 of the lower windowpane 6370. Although FIGS. 63 a and 63 bshow a VGU with spacers/stand-offs incorporated into the fabrication ofboth sides of the spacer unit 6350, in other embodiments, the stand-offsmay be incorporated into only the upper or lower surface of the spacerunit.

The spacer unit 6350 increases the thermal path of conduction betweenthe upper windowpane 6330 and lower windowpane 6370 when compared to thepreviously described and employed methods of separating the twowindowpanes. The sheet material of this spacer could be composed ofglass, plastic sheet or film. The spacer stand-offs 6351 and 6353 couldbe made from a multitude of materials. As previously discussed, thespacers would preferably be made from a low thermal conductivitymaterial. This spacer unit 6350 may be manufactured as a single piece ormay be composed of a sheet or film material with the stand-offs laterapplied to it by means that include those mentioned previously in thedescription of the attachment of spacers 5840 for FIGS. 58 a and 58 b.

FIGS. 64 a and 64 b show, respectively, an exploded view and anassembled view of a VGU in accordance with yet another embodiment. TheVGU 6400 is generally similar to the VGU 6300 previously describedherein, however, it comprises a side shield member disposed between thesealed frame members and the windowpanes. The VGU 6400 comprises anupper windowpane 6430 having a top surface 6431 and bottom surface 6433,and a lower windowpane 6470 having a top surface 6471 and a bottomsurface 6473. A spacer unit 6450 includes stand-offs 6451 on the uppersurface and stand-offs 6453 on the bottom surface. The spacer unit 6450is placed between the windowpanes 6430 and 6470 to maintain theseparation between them. The side shield members 6402 are disposed alongthe sides of the windowpanes and spacer. The side shield members 6402preferably have low thermal conductivity. In some embodiments, theshield members may be included for cosmetic purposes, e.g., to concealthe inner frame parts from observation through the windowpanes. In otherembodiments, the shield members 6402 comprise “getters” (i.e., getteringmaterial), which absorb or otherwise immobilize stray atoms or moleculesin the vacuum space within the VGU. Even if the VGU is hermeticallysealed, such atoms or molecules may appear in the vacuum due toout-gassing of one or more of the materials used on or inside the VGU.Such atoms or molecules may also come into the space contained withinthe VGU by slow penetration through an outside surface (e.g.,windowpanes and frame members), through the bonds/joints between framemembers and windowpanes and/or through the joint area of the upper andlower frame members.

The VGU 6400 is held together by an upper frame member 6410 and a lowerframe member 6490. The upper frame member 6410 has a top bonding surface6411 for hermetic bonding to the top surface 6431 of upper windowpane6430, an upper inside radius 6415, a lower outside radius 6417 and abottom bonding surface 6413. The lower frame member 6490 includes a topsurface 6491 for hermetic bonding to the lower bonding surface 6413 ofthe upper frame member 6410, and for hermetic bonding to the bottomsurface 6473 of the lower windowpane 6470.

FIGS. 65 a and 65 b show, respectively, an exploded view and anassembled view of a VGU in accordance with a still further embodiment.The VGU 6500 is generally similar to the VGU 6400 previously describedherein, however, it comprises upper and lower frame members that have asimilar shape and size. The VGU 6500 comprises an upper windowpane 6530and a lower windowpane 6570. A spacer unit 6550 includes stand-offs 6551on the upper surface and stand-offs 6553 on the bottom surface. Thespacer unit 6550 is placed between the windowpanes 6530 and 6570 tomaintain the separation between them. Optional side shield members 6502may be used along the sides of the windowpanes and spacer, however,these are not required. The VGU 6500 is held together by an upper framemember 6510 and a lower frame member 6590. Preferably, the upper andlower frame members 6510 and 6590 have identical shapes. This results inseveral advantages, including a reduction in parts count and processsteps. The upper frame member 6510 has a top bonding surface 6511 forhermetic bonding to the top surface 6531 of upper windowpane 6530 and abottom bonding surface 6513. The lower frame member 6590 includes a topsurface 6591 for hermetic bonding to the lower bonding surface 6513 ofthe upper frame member 6510, and a bottom bonding surface 6593 forhermetic bonding to the bottom surface 6573 of the lower windowpane6570.

FIGS. 66 a, 66 b and 66 c show three variations on frame member'scross-sectional form. Such frame members may be used for upper framemembers as illustrated in FIGS. 58 a-5 a, 63 a and 64 a, or as bothupper and lower frame members when symmetrical frame members are used asillustrated in FIG. 65 a. FIG. 66 a shows a frame member 6620 with tworadii (denoted 6621 and 6622), as has been previously illustrated.Having more than two radii in the vertical component of the frame membermay enable the frame member to be more compliant. FIG. 66 b shows aframe member 6640 with four radii (denoted 6641, 6642, 6643 and 6644),and FIG. 66 c shows a frame member 6660 with six radii (denoted 6661,6662, 6663, 6664, 6665 and 6666).

FIGS. 67 a through 67 f illustrate a muntin assembly suitable for use asthe spacer assembly to maintain windowpane separation in a VGU, as wellas for cosmetic appearances. Referring first to FIG. 67 a, there isillustrated a muntin grid unit 6751 comprising a first plurality ofparallel muntin bars 6752 disposed perpendicularly to a second pluralityof parallel muntin bars 6754. FIG. 67 b illustrates a muntin assembly6750 comprising the muntin grid unit 6751 and a plurality ofspacers/stand-offs 6753 and 6755 (see FIG. 67 c) disposed on at leastone side surface of the muntin grid unit. FIG. 67 c illustrates a sideview of the muntin assembly 6750 having stand-offs 6753 and 6755 on bothsides. FIG. 67 d is an exploded view, in perspective, of the muntin barassembly 6750 disposed between an upper VGU windowpane 6730 and a lowerVGU windowpane 6770. FIG. 67 e is a perspective view of the muntin barassembly 6750 disposed between, and in contact with the upper windowpane6730 and the lower windowpane 6770. FIG. 67 f is a side view of themuntin bar assembly 6750 disposed between the upper windowpane 6730 andthe lower windowpane 6770.

FIGS. 67 g and 67 h show, respectively, an exploded view and anassembled view of a VGU in accordance with yet another embodiment. TheVGU 6700 comprises the upper windowpane 6730 having a top surface 6731and the lower windowpane 6770 having a bottom surface 6773. The muntinassembly 6750 having stand-offs on the upper and lower surface isdisposed between the windowpanes 6730 and 6770 to maintain theseparation between them. The VGU 6700 is held together by an upper framemember 6710 and a lower frame member 6790. The upper frame member 6710has a top bonding surface 6711 for hermetic bonding to the top surface6731 of upper windowpane 6730 and a bottom bonding surface 6713. Thelower frame member 6790 includes a top surface 6791 for hermetic bondingto the lower bonding surface 6713 of the upper frame member 6710, andfor hermetic bonding to the bottom surface 6773 of the lower windowpane6770. Optionally, interlayers, 6720 and 6780 may be used to facilitatebonding of the upper and lower frame member to the respectivewindowpanes.

FIGS. 68 a and 68 b show a VGU 6800 with an internal muntin assembly6850 and with frame members 6810 and 6890 bonded to the inner (inside)surfaces of the upper and lower windowpanes 6830 and 6870, respectively.Mounting frame members 6810 and 6890 to the inner (inside) surfaces ofthe upper and lower windowpanes 6830 and 6870 may be done when there issufficient space between the two windowpanes to accommodate thethickness of the two frame members. The muntin assembly 6850 illustratedin this embodiment provides the necessary space. FIG. 68 a is anexploded view of the VGU with the upper and lower frame members 6810 and6890 bonded to the inner (inside) surfaces of the windowpanes 6830 and6870. FIG. 68 b is the assembled VGU with its frame members bonded tothe inner (inside) surfaces of the windowpanes.

FIGS. 69 a and 69 b show a VGU 6900 with an internal muntin assembly6950 and with inside-the windowpane bonded frame members 6910 and 6990that extend past (i.e., above and below) the outer surfaces of the upperand lower windowpanes 6930 and 6970. This is in contrast to FIGS. 68 aand 68 b, in which the inside-the windowpane bonded frame members 6810and 6890 do not extend above or below the outer surfaces of therespective upper and lower windowpanes 6830 and 6870.

FIGS. 70 a and 70 b show a VGU 7000 with inside-the-windowpane bondedframe members 7010 and 7090, similar to those of FIGS. 68 a and 68 b.The VGU 7000 includes optional upper and lower interlayers 7020 and 7040disposed between the respective upper and lower frame members 7010 and7090 and the respective upper and lower windowpanes 7030 and 7070 tofacilitate and/or enhance bonding. FIG. 70 a is an exploded view of VGU7000 with inside-the-windowpane bonded frame members and optionalinterlayers between the frame members and the windowpanes. FIG. 70 b isthe assembled view of the VGU. It will be appreciated that theinterlayers 7020 and 7040 may or may not actually be visible afterbonding, depending upon whether the interlayer material has beencompletely incorporated into the bond.

FIGS. 71 a, 71 b and 71 c illustrate examples of VGUs using anadditional, intermediate frame members bonded to the center spacerassembly. In some cases, using these additional frame members providesadded benefits to the VGU. Specifically, FIG. 71 a illustrates a VGU7101 comprising upper and lower windowpanes 7130 and 7170, a centerspacer unit 7150, and upper and lower frame members 7110 and 7190,similar to that of FIGS. 63 a and 63 b.

FIG. 71 b illustrates a VGU 7102, similar to VGU 7101, except the spacerunit (now denoted 7150 a) extends past the sides of the upper windowpane7130 and lower windowpane 7170, and the lower frame member (now denoted7190 a) has also been extended. This configuration provides the exposedsurface area on both the top and bottom of spacer unit 7150 a to attachcenter frame member 7140 onto either surface, and provides additionalspace on the lower frame member 7190 a to allow bonding of both anextended upper frame member 7120 and the center frame member. In theillustrated embodiment, the center frame member 7140 is shown attachedto the top surface of the spacer unit 7150 a, but it may be attached tothe bottom surface in other embodiments.

FIG. 71 c illustrates a VGU 7103, similar to VGU 7102, except that boththe spacer unit 7150 a and the lower windowpane (now denoted 7170 a)extend past the sides of the upper window unit 7130. Again, intermediateframe member 7140 is attached to the top surface of the spacer unit 7150a.

FIGS. 72 a and 72 b show, respectively, an exploded view and anassembled view of a VGU in accordance with yet another embodiment. TheVGU 7200 is similar to that described in connection with FIGS. 65 a and65 b, except in this embodiment a flat spacer sheet 7250 of transparentmaterial is positioned between the windowpane sheets 7230 and 7270, andthe stand-offs 7255 are built-on to the inner surfaces of the windowpanesheets. The stand-offs 7255 may be formed as an integral part of thewindowpanes 7230 and 7270 (e.g., molded on or embossed duringmanufacturing) or they may be applied to the windowpane separately(e.g., by adhesive) after manufacture of the windowpane. The latteroption, i.e., post-manufacture attachment of the stand-offs, allows theinner surfaces of the windowpanes 7230 and 7270 to be coated (e.g., withlow-emissivity or other coatings) while still flat, with the stand-offs7255 being applied after coating. The spacer sheet 7250 may be made ofglass, plastic sheets or films, or other transparent materials. Thespacer sheet 7250 may be made of a material which inherently has specialemissivity, insulating, or other physical properties (e.g., breakageresistance), or it may be coated with other materials to provide thedesired properties. The upper and lower frame members 7210 and 7290 arediffusion bonded to the windowpanes 7230 and 7270 as previouslydescribed. Optional seal/getter members 7202 may be provided within thepackage as previously described.

It will be appreciated that alternative windowpane shapes may be used.The pairs of windowpanes do not need to be flat. They may be concave orconvex in shape. Each of the windowpanes may have a different shape, aslong as each windowpane mates intimately with the frame member, e.g.,during the bonding process, the surface of glass is in intimate contactwith the surface of the frame member to which it is bonded.

It will also be appreciated that alternative windowpane materials may beused. The windowpane material need not be glass. It could be a differenttransparent or non-transparent material, including, but not limited toquartz, sapphire, silicon and even metals, metal alloys, and ceramics.

As an alternative to conventional diffusion bonding chambers withinternal rams, another apparatus that is suitable for diffusion bondingthe windowpanes to the strength-reinforcing layers to form laminatedstrength-reinforced window assemblies is known as a Hot Isostatic Press(“HIP”). A HIP unit provides the simultaneous application of heat andhigh pressure. In the HIP unit, the work pieces (e.g., the windowassembly components) are typically sealed inside a vacuum-tight bag,which is then evacuated. The bag with work pieces inside is then sealedwithin a pressure containment vessel or apparatus, which in turn is apart of, or is contained within, a high temperature furnace. A gas,typically argon, is introduced into the vessel around the bagged partsand the furnace turned on. As the furnace heats the pressure vessel, thetemperature and pressure of the gas inside simultaneously increase. Thegas pressure supplies great force pressing the bagged parts together,and the gas temperature supplies the heat necessary to allow bonding tooccur. A HIP unit allows the temperature, pressure and process time toall be controlled to achieve the optimum material properties.

In some embodiments, the CTE's of the materials to be bonded togethermay be matched. The Coefficient of Linear Thermal Expansion (CTE) of theframe material(s) must be properly matched to the glass windowpanes towhich the frame is bonded. The CTE of most glasses is fairly constantfrom approximately 273° K (0° Centigrade) up to the glass' softeningtemperature. However, some metals and alloys have different CTEs atdifferent temperatures.

The average CTE of the frame material(s) from the elevatedglass-to-frame bonding temperature should be closely matched to that ofthe glass' average CTE over the same temperature range. The closer theaverage CTEs of the two materials, the lower will be the residualstresses in the frame and the glass windowpanes after the assembly coolsfrom the elevated bonding temperature back to ambient (roomtemperature).

Also critical for long-term reliability of the frame-to glass seal insome embodiments is the close matching of the CTEs of the framematerial(s) to the glass for the anticipated end-use environment. Forexample, if the window assembly is expected to be exposed totemperatures from minus 40° C. to plus 100° C. (minus 40° F. to plus212° F.) then the frame material(s) and the glass material should haveclosely matched CTEs over this temperature range.

In many embodiments, it is desirable that if CTE of the frame'smaterial(s) cannot be exactly matched to the CTE of the glass material,then the CTE of the frame's material(s) should be slightly greater thanthat of the glass. In this situation where the CTE of the framematerial(s) exceeds that of the glass, the frame would contract morethan the glass during cool-down from the elevated bonding temperatureback to ambient, resulting in the glass being in slight compression.This is preferable to the glass being in tension, since glass in tensionis prone to cracking.

There are other methods than diffusion bonding that could be employed toattach hermetically the frame member to the windowpane of the VGU. Theseinclude: using solder glass, employed primarily between the frame memberand the windowpane where the two are to be joined, and then localized orglobal heating the two parts to form a solder joint; and localized orglobal heating the two parts to from a fusion joint. Although these andother methods may be used to attach frame members to a windowpane inconstruction of the described and illustrated VGUs, the preferred methodof attachment is diffusion bonding and/or transient liquid phasediffusion bonding.

The current invention uses an established, commercially available,technology called diffusion bonding for a proprietary, patent pendingapplication to hermetically join glass windowpanes directly to theircompliant (spring-like) metal or metal alloy sleeve/frame component. Noglues, adhesives or epoxy materials will be used between the glass andframe component. The attachment will be permanent and more hermetic(gas-tight) than any other attachment method.

Referring now to FIGS. 73 a and b, the components of one embodiment of avacuum-containment IG unit are illustrated, FIG. 73 a being an explodedview and FIG. 73 b being an assembled view. The IGU 7300 comprises anupper windowpane (i.e., lite) 7330 and a lower windowpane 7370 separatedby a transparent spacer unit 7350 disposed therebetween. The edges ofthe windowpanes 7330 and 7370 are hermetically sealed together usingmetal or metal alloy frame components 7310 and 7390 as further describedbelow. The cavity between the windowpanes 7330 and 7370 contains avacuum or partially evacuated atmosphere.

Referring now to FIG. 73 c, one embodiment of the compliant metalframe/sleeve member 7310 and 7390 is shown. It is designed to beflexible in all three axes, allowing the glass lites 7330 and 7390 toexpand and contract independently of each other without them or thesleeve-to lite bond region experiencing any significant stresses. Thusit acts similar to an accordion bellows, expanding and contracting as itis pulled and pushed. This sleeve unit can be made to extend very littlefrom the sides of the upper and lower windowpanes.

Item 7302 is shown as an optional feature of the IGU 7300. It is agettering material, such as is made by SAES Getters. Getters are used inhigh reliability hermetic packaging to absorb atoms and molecules thatare outgased from materials, or to absorb any gas that might leak intothe package over an extremely long period of time.

The spacer unit 7350 is preferably formed of transparent glass, but mayalso be formed of transparent polymer materials such as plastics orresins. In certain embodiments described herein, other transparentmaterials may be used. The spacer unit 7350 comprises a sheet-likesubstrate portion 7352 having integrally-formed stand-offs (also knownas “pillars”) 7354 projecting from one and/or both sides of thesubstrate portion. The structure may be similar to a plastic chair matfound in offices on the carpet under roller chairs, except that it mayhave stand-offs on both its top and bottom surfaces. The stand-offs 7354are disposed generally evenly across the surface of the substrateportion 7352 so as to provide generally even support to the adjacentwindowpane. When viewed from above, the stand-offs 7354 will preferablybe disposed in an orderly array (see FIGS. 77-79), however, this is notrequired as long as they provide adequate support to prevent thewindowpane from cracking.

For purposes of this application, the term “integrally formed” is usedto mean that the stand-offs 7354 are formed by manipulating the body ofthe substrate portion 7352 itself, e.g., by casting, embossing,stamping, etching, etc., rather than by first forming the stand-offsseparately from the substrate portion and then attaching them onto thesubstrate portion later. While the stand-offs 7354 and substrate portion7352 will generally be composed of the same material when formed, thestand-offs and/or the substrate portion may be further processed, e.g.,by heat treatment, chemical treatment, polishing, etc., to modify theircharacteristics after formation.

Referring now to FIG. 74, a spacer unit 7450 in accordance with oneembodiment is shown. The spacer unit 7450 comprises a transparentsheet-like substrate portion 7452 having integrally-formed stand-offs7454 projecting from one side. In this embodiment, the unit 7450 isformed of transparent glass, however, other materials may be used inother embodiments.

Referring now to FIG. 75, a spacer unit 7550 in accordance with anotherembodiment is shown. The spacer unit 7550 comprises a transparentsheet-like substrate portion 7552 having integrally-formed stand-offs7554 projecting from both sides of the substrate portion. The unit 7550is this embodiment is also formed of transparent glass, however, othermaterials may be used in other embodiments.

Referring now to FIG. 76, a spacer unit 7650 in accordance with yetanother embodiment is shown. In this embodiment, the spacer unit 7650has a substrate portion formed of multiple discrete layers. A top layer7655 includes an upper substrate portion 7656 with integral upperstand-offs 7657, similar to that previously described in FIG. 74. Abottom layer 7658 includes a lower substrate portion 7659 with integrallower stand-offs 7660, also similar to that previously described,although it is not necessary that the top layer 7655 and bottom layer7658 be formed of the same material. Disposed in a “sandwiched”configuration between the upper and lower substrate portions 7656 and7659 is a layer of discrete material 7661. In this embodiment, the topand bottom layers 7655 and 7658 are formed of transparent glass, whilethe middle layer 7661 is formed of a transparent plastic material suchas Lexan. The discrete material layer 7661 may have different thermalconductivity, sound transmission, breakage resistance or otherproperties than the adjacent layer(s). The discrete material may be aglass, plastic, polymer, resin, adhesive or other material. Its form maybe that of a free-standing sheet or film, or it may be a material thatis sprayed on or otherwise applied to the free surface (i.e., the onewithout stand-offs) of one of the substrate portions. It will beappreciated that, while the embodiment shown includes three layers,other embodiments could include only two layers, e.g., only the toplayer 7655 and the discrete layer 7661, or only the bottom layer 7658and the discrete layer 7661, or only the top layer 7655 and the bottomlayer 7658. Similarly, multiple discrete internal layers (i.e., withoutstand-offs) could be used to provide the spacer-unit 7650 with four ormore total layers.

In some embodiments, performance-enhancing coatings may be “embedded”within the multi-layer laminated spacer 7650. For example, coatings maybe applied to the inner surfaces of the upper substrate portion 7656and/or lower substrate portion 7659, or to the surfaces of center layer7661. These coatings may include low-emissivity coatings, U-V absorbingor reflecting coatings, color tints, electrochromatic coatings,electrochromeric coatings, anti-reflective coatings and/or otherperformance-enhancing coatings. After the coatings are applied to thedesired surface, the layers of the spacer 7650 are laminated together.In this manner, the coatings, which are often very thin films, areprotected from physical damage caused by relative movement between thewindowpanes and the spacer. If the same coating was applied to theinside surface of the windowpane, it could be damaged by contact and/ormovement of the stand-offs on the spacer unit.

Referring again to FIGS. 74, 75 and 76, performance-enhancing coatingsmay be applied to either side of the spacer units, e.g., spacer-units7450, 7550, and 7650, instead of to the inner surfaces (i.e., surfaces#2 and #3) of the window panes themselves. These coatings on the spacerunit may include low-emissivity coatings, U-V absorbing or reflectingcoatings, color tints, electro-chromatic coatings, anti-reflectivecoatings and/or other performance-enhancing coatings. In some cases, allcoatings will be applied to a single side of the spacer unit, while inother cases selected coatings may be applied on a first side of thespacer unit, and other coatings may be applied to the other side of thespacer unit. In the case of multi-layer spacer units 7650 (e.g., FIG.76), coatings may be placed on the free side of the substrate portionsand/or on the intermediate layers.

Placing the performance-enhancing coatings on the spacer unit 7450, 7550or 7650 may be advantageous because the spacer system (i.e., spacerunit) will often be at a different temperature than either the bulk ofwindow #1 or window #2, and as such, will be expanding and contactingfrom its center less than window #1 and more than window #2. Havingcoatings, such as low-e, on the spacer's substrate surfaces instead ofthe IG unit's surfaces #2 and/or #3 will eliminate the potential of thecoatings being scratched and damaged by the differential movements ofthe IG Unit's components. In addition, special coatings may be used toenhance the durability of surfaces #2 and #3, in order to reduceabrasion by the movements of the spacer stand-offs. Coatings such asdiamond-like coatings (DLC) will be used to ensure that the glasssurfaces remain scratch-free for long periods of time. DLC and othercoatings are already in use to provide scratch resistance and resistanceto other damage. Another advantage of the proposed spacer system is thatthe thicker the spacer's substrate, the greater will be the unit'sthermal resistance, and thus, the overall insulating value of theresulting IG unit.

The stand-offs of the spacer unit, e.g., spacer 7450, 7550 or 7650 mayhave cross sections (when seen from above) that are circular, tapered,or of other shapes. Referring now to FIGS. 77 and 78, in someembodiments, the stand-offs may have a cross-section (seen from above)resembling a cross or “plus” sign (“+”) to provide the physicalseparation between the inside surfaces of the IG unit's windowpanes(surfaces #2 and #3) and the substrate portion of the spacer unit. Inthe embodiment shown in FIG. 77, the spacer unit 7750 includes asubstrate 7752 and a plurality of stand-offs 7754, all made of glass andintegrally formed. The “+” shaped standoffs 7754 have horizontal andvertical members that are about 0.5″ in length, and their wall thicknessand height are within the range from about 25 microns to about 50microns (0.001″ to 0.002″). An average human hair is about 75 microns(0.003″) thick. The extremely small width and height of the glassstand-offs, along with their transparency, will make them practicallyinvisible. In the embodiment shown in FIG. 78, the spacer unit 7850 alsocomprises a substrate 7852 and a plurality of “+” shaped stand-offs7854. Both are made of glass, however, in this embodiment, the substrate7852 is formed as a flat sheet, and then the stand-offs 7854 are affixedonto the substrate later.

Referring now to FIG. 79, in an alternative embodiment, the spacer unit7950 comprises stand-offs 7954 having a cross-section resembling theletter “C” that are arranged in an array across the surface of thesubstrate portion 7952. The standoffs can be of any shape and size aslong as they are strong enough to support the force of the IGU'swindowpanes pressing inward due to the atmospheric pressure's force onthe outside of these two windowpanes.

The standoffs must also be strong enough (of adequate materialcomposition and dimensions) so as to retain their size enough that theycontinue to function as required to keep the two windowpanes from cominginto contact with the substrate of the spacer unit, and thus provide adirect thermal path. Also, the standoffs must be designed to have enoughsurface area so that the static load on the windowpanes they'resupporting does not cause either windowpane to crack, break or otherwisefail.

It is desirable to minimize the overall area of contact between thespacer unit and windowpanes in order to minimize the conductive paththrough the spacer system and maximize the insulating value of the IGunit. However, spacers may experience extremely high loading (pressure)from windows #2 and #3 on their surface because the outside of the IGunit is at 14.7 psi (ambient or 1 atmosphere air pressure) while theinside of the unit, with its vacuum, is at near zero psi. Accordingly,the surface area for each stand-off must be selected such that theirarea loading on the windows #1 and #2 would not produce micro-cracks orbreak the windows, or compress them to a point where they would not bemaintaining the separation intended.

In one embodiment, IGUs may be assembled as follows: First, the flexible(i.e., compliant) metal sleeves (also called “bellows”) are hermeticallybonded to windows #1 and #2 to make window sub-assemblies. Next, thespacer system (if used) is placed in between the two windowsub-assemblies. Next, the sleeves are hermetically bonded together in avacuum, so that the entire IG unit is sealed in this vacuum and will notrequire an evacuation tube and a post-assembly evacuation step. Whilediffusion bonding is preferred for the hermetic bonding, other methodssuch as solder glass bonding may be used in some embodiments.

Either electrical resistance seam welding or laser welding are amongalternatives to hermetically seal the sleeves to each other. A primeconsideration for this step is to minimize the heat-affected zone so asnot to thermal shock and crack the glass lites. Moderating the heat rateof either process will alleviate this possibility. In addition, copperplates or other material could be placed on the top and bottom surfacesof the unit to act as a heat sink during the sealing process.

Referring now to FIG. 80, there is illustrated an insulated glass unit(IGU) having a floating spacer unit that maintains separation of thelites (i.e., windowpanes). The IGU 8000 includes lites 8002 and 8004,which are spaced apart from one another by spacer 8006. The gap or space8008 between lites 8002 and 8004 may be filled with a gas or gas mixtureor it may contain a vacuum or partial vacuum to yield the desiredinsulating properties. Flexible sleeves 8010 and 8012 are hermeticallybonded to lites 8002 and 8004, respectively, at one end and arehermetically bonded to one another at the other end to keep the fill-gasor gas mixture (or vacuum) inside the IGU space 8008. The spacer 8006 isallowed to float, i.e., it is not bonded to both of the lites, althoughit may be bonded by adhesive or other means to one of the two lites. Theposition of the spacer 8006 between the two lites 8002 and 8004 ismaintained by retaining rods, or bars, 8014 so that it stays in positioncentered between the two lites. Each retaining bar 8014 is attached tothe spacer 8006 at one end and to the flexible sleeves 8010 and/or 8012at the other end. Preferably, the retaining bar 8014 is attached to theflexible sleeves by crimping therebetween, or other mechanical means,which will not affect the hermetic bond between the sleeves.

Referring now to FIG. 81, there is illustrated a three-pane IGU inaccordance with another embodiment. The IGU 8100 includes lites 8102,8104, and 8106. Preferably, the IGU 8100 is gas-filled. Compliant frames(i.e., bellows) 8108, 8110, and 8112 are hermetically bonded to one ofthe lites at a first end and then bonded to one or both of the otherframes at the other end to provide a hermetic seal for maintaining thefill-gas in the sealed spaces 8114 and 8116 between the lites. The IGU8100 relies on the mechanical strength of the frames 8108, 8110, and8112 (rather than a spacer) to maintain the desired spacing between thelites. Accordingly, this configuration may be less suitable for usewhere vacuum levels in spaces 8114 and 8116 and/or compressive loads onthe unit are high.

Referring now to FIG. 82, there is illustrated a three-pane IGU inaccordance with another embodiment suitable for use with higher vacuumlevels and/or compressive loads than the embodiment shown in FIG. 81.The IGU 8200 includes lites 8202, 8204, and 8206, each attached to arespective compliant frame 8208, 8210, and 8212. The frames arehermetically bonded to the lites at a first end and to each other at asecond end to maintain hermetically sealed spaces 8214 and 8216 betweenthe lites. As in the embodiment described in connection with FIG. 80,the spacers 8218 and 8220 float, i.e., they are not bonded to both ofthe adjacent lites, although they may be bonded to one of the twoadjacent lites. In the embodiment illustrated in FIG. 82, the spacer8218 is actually disposed on the inner end of the compliant sleeve 8210,accordingly, the height of spacer 8218 must be slightly less than theheight of spacer 8220 if the spacing between the lites is to beidentical. In other embodiments (e.g., FIG. 87) the spacer may bemounted inside the sleeve bonding area such that the two spacers mayhave the same thickness. The spacers 8218 and 8220 are held in positionby retainer bars 8222 and 8224, respectively, which extend from thespacers to the compliant frame as previously discussed. It will be notedthat the retainer bars 8222 and 8224 are preferably compliant to allowrelative movement with the lites.

Referring now to FIG. 83, the two-lite IGU 8000 of FIG. 80 is shown fromabove to illustrate further details. It will be appreciated that, forpurposes of illustration, the size of the window-area relative to theframe-area is very small; however, this is to better illustrate detailsof the frame, and should not be considered a limitation of theinvention. FIG. 83 shows how the lites 8002, 8004, and spacer 8006 arepositioned between the compliant frames or sleeves 8010 and 8012. Thecompliant frames are hermetically bonded to the glass lites alonginterior bonding surface 8310 and are bonded to one another alongexterior bonding surface 8312. The floating spacer 8006 is maintained inposition by retainer bars 8014, one or more of which may be mountedalong each edge of the spacer. The retainer bar inside end 8314 isattached to the spacer and the retainer bar outside end 8316 extendsoutward where it may be crimped or otherwise connected to the compliantframes 8010 and/or 8012.

Referring now to FIG. 84, there is illustrated a two-pane IGU inaccordance with another embodiment. The IGU 8400 is substantiallysimilar to that shown in FIGS. 80 and 83. It includes lites 8002 and8004 disposed on either side of a spacer 8406 to define an interiorspace 8008. Compliant frames or sleeves 8010 and 8012 are hermeticallybonded to the outside surfaces of the lites at one end and to oneanother at the other end to hermetically seal the fill-gasses in space8008. The spacer unit 8406 differs from the spacer 8006 shown in FIG. 80in that the spacer of this embodiment includes internal reinforcement8408. In the illustrated embodiment, the reinforcement 8408 comprises anX-shaped internal web, however, other configurations may be used.Preferably, the spacer 8406 is an extruded article having thereinforcement 8408 as an integrally formed part. The retaining bars 8014of this embodiment have contours designed to make them compliant suchthat the spacer 8406 may float with respect to the lites 8002 and 8004.The retaining bar 8014 further includes a connector feature 8410positioned at the interior end and adapted to connect to the spacer 8406as further described herein.

Referring now to FIGS. 85 and 86, an enlarged, cross-sectional view of aportion of the spacer unit 8406 is shown to better illustrate theinternal reinforcement and connection aspects of the current invention.The outer wall 8506 of the spacer includes a connector feature 8504adapted to cooperate with the connector feature 8410 of the retainingbar 8014. In the illustrated embodiment, the spacer connector feature8504 comprises a slot 8508 of width “w” formed in the wall 8506 and theretainer bar connector feature 8410 comprises a pair of spaced-apartdiscs 8510 and 8512 formed on the end of the retainer bar 8014. Thewidth “w” is selected to be sufficient to accept bar 8014, but the discs8510 and 8512 both have a diameter d>w. As best seen in FIG. 85, theconnector feature 8410 on the retainer bar 8014 can be moved into theconnector feature 8508 on the spacer as indicated by arrow 8514. In theconnected configuration shown in FIG. 86, the retainer bar 8014 isattached to the spacer 8406 to prevent movement in either direction.

Referring now to FIGS. 87 and 88, there is illustrated a three-lite IGUhaving internally bonded frames in accordance with another embodiment.The IGU 8700 includes lites 8702, 8704, and 8706 separated by spacers8708 and 8710 to form spaces 8712 and 8714. Compliant frames 8716, 8718,and 8720 are hermetically bonded at one end to the inner surfaces of thelites 8702, 8704, and 8706, respectively, and to one another at theouter ends to hermetically seal the fill-gas or vacuum in the spaces8712 and 8714. Retainer bars 8722 connected between the spacers andframes are used to hold the spacers in place with respect to the lites.

In the embodiment illustrated in FIG. 87, the spacers 8708 and 8710 areadapted to accommodate the internally bonded frames of IGU 8700. Theupper spacer 8708 is dimensioned to be slightly smaller than the widthof the lites, thereby being disposed inwardly of the inner frame endsand avoiding contact with the bonded frame ends. As best seen in FIG.88, the lower spacer 8710 has a stepped configuration within insetportions 8724 on the ends which allow the spacer to avoid contact withthe frame ends bonded to the adjacent inner surfaces of the lites 8704and 8706. It will be appreciated that the illustrated configurations areonly examples, and not limiting. Many other configurations forinternally and externally mounting compliant frames will be understoodto be within the scope of the invention.

Referring now to FIGS. 89 through 93, there are illustrated IGUs withholding blocks in accordance with additional embodiments. The holdingblocks are adapted to support a significant fraction of the weight of anIGU having flexible sleeves (i.e., frames) when the IGU is mountedvertically in a window or doorframe system. Preferably, the holdingblock will be configured to minimize contact with the flexible sleeve soas to reduce thermal transfer therebetween. This also allows the sleeveto move as necessary to accommodate relative movement of the windowlites.

Referring first to FIG. 89, there is illustrated a two-lite IGU suitablefor use with a holding block. The IGU 8900 comprises lites 8902 and 8904separated by spacer unit 8906. In this embodiment, the spacer unit 8906comprises a transparent sheet 8908 having a plurality of stand-offs 8910projecting from each side. Compliant frame members 8912 and 8914 arehermetically bonded to the inner surfaces of the lites 8902 and 8904 ata first end 8916, and hermetically bonded to one another at a second end8918 to form the hermetically sealed cavity 8920 between the lites. Thespacer unit 8906 may be held in position using retainer bars (not shown)as previously described, or using other means described herein.

Referring now to FIG. 90, there is illustrated the IGU 8900 installed ona holding block. When viewed on end, the holding block 9000 is seen toinclude a base-portion 9001 and riser portions 9002 and 9004 projectingupwardly from the base portion to define a sleeve cavity 9008. Eachriser portion 9002 and 9004 has a bearing surface 9010 disposed at theupper end. The holding block 9000 is dimensioned such that when the IGU8900 is positioned on the block, the edges of the lites 8902 and 8904are supported on the bearing surfaces 9010 of their respective risers9002 and 9004, and the compliant sleeves 8912 and 8914 (which arehermetically bonded together) are positioned within the sleeve cavity9008. Preferably, the bonded sleeves 8912 and 8914 will not touch thewalls of the cavity 9008 so that their movement will not be constrainedand so as to minimize thermal transfer. However, a significant fraction(if not all) of the weight of the IGU will be supported by the riser andbase portions of the block. The holding block 9000 may be formed ofmetals such steel or aluminum, but preferably is formed of a non-metalmaterial having lower thermal conductivity, e.g., wood, vinyl, PVC,fiberglass, polyethylene, etc. Although not required, in a preferredembodiment, the holding block 9000 will be formed by extrusion. In otherembodiments, rolling, milling, routing or other forming processes may beused to form the holding block.

Referring now to FIG. 91 a, the IGU 8900 and holding block 9000 areillustrated after installation in a channel frame, such as a buildingwindow frame or doorframe. The channel frame 9100 includes a baseportion 9101 and riser portions 9102 and 9104 projecting upwardly fromthe base to define a channel 9108. The channel frame 9100 is dimensionedsuch that the entire holding block 9000 and a portion of the IGU 8900fit within the channel 9108. In this manner, the channel frame 9100provides both vertical and horizontal support for the IGU 8900. Thechannel frame 9100 may be formed of metals such as steel or aluminum,but preferably is formed of a non-metal material having lower thermalconductivity, e.g., wood, vinyl, PVC, fiberglass, polyethylene, etc.

It will be appreciated that the channel frame 9100 may be a conventionalU-shaped window frame or doorframe. In such cases, the holding block9000 acts as an adapter to allow the IGU 8900 having external compliantseal frames (e.g., frames 8912 and 8914) to be installed in newconstruction or in an existing structure.

Referring now to FIG. 91 b, it will further be appreciated that in someembodiments, the holding block and the channel frame may be combinedinto a unitary combine frame. Combined frame 9150 is one example of aunitary frame and holding block. A combined frame may be used in newconstruction for the support of IGUs (e.g., IGU 8900) with externalcompliant frames without requiring a separate holding block.

Referring now to FIG. 92, there is illustrated a perspective view of aholding block of one embodiment. The holding block 9200 is substantiallysimilar in cross-section to block 9000 previously described. The block9200 is preferably formed by extrusion, although other known methods offabrication may be used. The block 9200 has a length, denoted L, whichin some cases may be equal to the length of the associated IGU. In othercases, however, the length L may be only a fraction of the length of theIGU, and multiple blocks 9200 may be disposed along the edge of the IGUfor support.

Referring now also to FIG. 93, to provide additional insulation effect,thermal break slots 9202 may be formed through the base portion 9001 ofthe holding block 9200. These slots reduce the cross-sectional area ofthe material connecting the sides of the block 9200 to reduce heattransfer from one side of the block to the other.

Referring now to FIG. 94 a, there is illustrated a two-pane IGUincorporating anchor spacers in accordance with another embodiment. TheIGU 9400 includes panes (i.e., “lites”) 9402 and 9404 separated by aspacer unit 9406 to form a gap cavity 9408. Compliant frames 9410 and9412 are hermetically bonded to the interior surface of the panes 9402and 9404 at one end, and are hermetically bonded together at the otherend. Spacer anchors 9414 are provided at each end of the spacer 9406,extending into the cavity 9416 between the frame members 9410 and 9412.The spacer anchors 9414 have profile features that trap a portion of theanchor within the compliant frame cavity 9416 when the IGU is assembled.

In the illustrated embodiment, the profile features includenotched-proximal end 9418, which accommodates the width of the innerends of the frames members 9410 and 9412, and a flared distal end 9420which has an expanded profile that substantially fills the width betweenthe frame members as they extend from the inner bonding point. It willbe appreciated that many other profile features could be used dependingon the profiles of the frame members.

During assembly of the IGU 9400, the frame members 9410 and 9412 arefirst hermetically bonded to their respective panes 9402 and 9404. Next,the spacer 9406 with anchors 9414 is placed in positioned between thetwo sub-assemblies. The two window sub-assemblies are then hermeticallybonded together along the outer frame joint, thereby trapping theanchors 9414 in place between the frame members 9410 and 9412. Thetrapped spacer anchors 9414 prevent the spacer 9406 from moving anysignificant distance in either direction between the two window panes.

The configuration illustrated in FIG. 94 a is typical of a gas-filledIGU having an “open” spacer unit 9406 (see, e.g., FIG. 83). In suchIGUs, the pressure differential across the windowpanes is low enoughthat direct support is not required for the interior portions of thewindowpanes. In other embodiments, however, including low pressure IGUsor vacuum IGUs (i.e., VGUs), direct support of the interior portions ofthe windowpanes is required. In such embodiments, an IGU substantiallysimilar to IGU 9400 may be used, except that the open spacer unit 9406having spacer anchors 9414 may be replaced with a stand-off type spacerunit (e.g., such as shown in FIGS. 63 a-65 a, 74-76 or 89-91 a) havingspacer anchors 9414. The stand-off type spacer is placed between thewindowpanes to maintain their separation, and the contoured spaceranchors 9414 are attached to the edges of the spacer to maintain theposition of the spacer between the windowpanes by locking into thecavity between the frame members as previously described.

Referring now to FIG. 94 b, there is illustrated an IGU having no spacerat all in accordance with another embodiment. The IGU 9450 includespanes 9452 and 9454, which are spaced apart from one another to form agap cavity 9458. Compliant frames (i.e., bellows) 9460 and 9462 arehermetically bonded to the interior surface of the panes 9452 and 9454at one end, and are hermetically bonded to each other at the other end.Although compliant, the frames 9460 and 9462 along the sides of the IGUmay provide enough mechanical stiffness (or “spring”) to maintainseparation of the panes 9452 and 9454 without requiring mechanicalspacers. In such cases, a separate spacer unit, whether an open unitdisposed around the periphery of the cavity or a stand-off unit disposedbetween the panes, may not be required. Typically, IGUs not having aninternal spacer unit will be gas- or air-filled insulating glass units,since the gas pressure within the cavity 9458 will reduce thedifferential pressure across the panes, thereby reducing the stiffnessrequired in the frames 9460 and 9462 to maintain separation.

Referring now to FIG. 95, there is illustrated a three-pane IGUincorporating split anchor spacers in accordance with yet anotherembodiment. The IGU 9500 includes panes (i.e., “lites”) 9502, 9503 and9504 separated by a spacer units 9506 and 9507 to form a gap cavities9508 and 9509. Compliant frames 9510 and 9512 are hermetically bonded tothe interior surface of the outer panes 9502 and 9504 at one end, andare hermetically bonded together at the other end. Spacer anchors 9514are provided at each end of the spacer 9506 and 9507, extending into thecavity 9516 between the frame members 9510 and 9512. The spacer anchors9514 of this embodiment are similar in most ways to the two-pane anchors9414 previously described. However, the spacer anchors 9514 of thisembodiment have different profile features on each side. In particular,when the IGU is assembled, the outward facing surfaces have features9517 and 9518 that trap a portion of the anchor within the compliantframe cavity 9516, and the inward facing surfaces have features 9520that support the center pane 9503.

During assembly of the IGU 9500, the frame members 9510 and 9512 arefirst hermetically bonded to their respective outer panes 9502 and 9504to form outer window sub-assemblies. Next, the spacers 9506 and 9507with split anchors 9514 are placed on either side of the center pane9503 to form a center sub-assembly. The center sub-assembly is nextpositioned between the two outer window sub-assemblies. The two outerwindow sub-assemblies are then hermetically bonded together along theouter frame joint, thereby trapping the anchors 9514 (with theassociated spacers and the center pane) in place between the framemembers 9510 and 9512. The trapped spacer anchors 9514 prevent thespacers 9506 and 9507, and the center pane 9503, from moving anysignificant distance in either direction between the two outer windowpanes.

Referring now to FIGS. 96 a, 96 b and 96 c, there is illustrated an IGUthat includes flexible metal sleeves attached to the outside-facing orinside-facing surfaces of glass windowpanes in accordance with yetanother embodiment. Whereas the flexible sleeve systems previouslydescribed herein have a flexible portion that extends past the outsideperimeter of the windowpanes to which they are attached, in thisembodiment the flexible components of the IGU are hermetically attachedto the inside facing surfaces of the two windowpanes (i.e., industrynomenclature surfaces #2 and #3), and the flexible portions are “flush”with the outside perimeter, i.e., disposed substantially within theoutside perimeter of the IGU. The hermetic attachment may be bydiffusion bonding or through the use of solder glass. This configurationmay look similar to known gas-filled IGUs that use a spacer along theinside perimeter, however the current embodiment has significantdifferences. First, the flexible metal spacer is diffusion bonded orattached via solder glass to form a hermetic attachment to theinside-facing surface of each of the two windowpanes. Known IGU systemsemploy a non-hermetic adhesive or epoxy to bond the spacer unit to theinsider of the windowpanes. Second, the spacer in this concept isflexible in all three axes, X, Y and Z, to allow the two windowpanes toexpand and contract due to the effects of temperature changes on bothsides of the IGU (i.e., inside the wall and outside the wall containingthe IGU). When there is significant pressure differential between theinside and outside of the IGU (e.g., when the IGU contains a vacuum orreduced-pressure gas), a transparent spacer system must be used in theIGU to keep the panes mechanically separated. The spacer system alsoprovides the depth required for the flexible sleeves to reside betweenthe windowpanes.

Referring now specifically to FIG. 96 a, in the illustrated embodimentthe IGU 9600 comprises an upper lite 9602, upper flexible frame member9604, lower flexible frame member 9606 and lower lite 9608. It will beappreciated that the frame members 9604 and 9606 are dimensioned to fitwithin the outside perimeter of the lites, and each frame member hasupper and lower bonding surfaces. The outward bonding surface of each ofthe flexible frame members 9604 and 9606 is hermetically attached to therespective lites 9602 and 9608, preferably using diffusion bonding orsoldering using solder glass, to form a pair of window sub-assemblies9612 and 9614.

Referring now to FIG. 96 b, a transparent spacer unit 9610 is placedbetween the window sub-assemblies 9612 and 9614. In the illustratedembodiment, the spacer unit 9610 comprises a transparent sheet with anarray of stand-offs on each side, however, the spacer units of otherembodiments may utilize other configurations previously describedherein. The inward bonding surfaces of the two sub-assemblies 9612 and9614 are next hermetically attached to one another, preferably usingdiffusion bonding or solder glass, thereby forming a hermetic cavitytherebetween and trapping the spacer 9610 within.

Referring now to FIG. 96 c, the completed IGU 9600 is shown. It will beappreciated that the frame members 9604 and 9606 do not extend beyondthe periphery of the lites. It will further be appreciated that thedesired atmosphere in the cavity of the IGU, e.g., vacuum,reduced-pressure atmosphere or fill-gas, may be placed in the IGU byvarious methods. First, the bonding of the two sub-assemblies 9612 and9614 may be performed directly in an appropriate atmosphere (e.g.,vacuum, reduced pressure, etc.) such that the desired fill is “trapped”in the cavity at bonding. Alternatively, a pinch-tube or other such port(not shown) may be incorporated into one of the frame members. In thiscase, the cavity may be evacuated and/or filled with the appropriatefill-gas via the pinch-tube after bonding. The pinch-tube may then behermetically sealed by known means.

It is envisioned that some embodiments of the invention will beinsulated glass units having metal sleeves and an electrochromatic orelectrochromeric coatings on one or more inside surfaces of thewindowpanes. An electrical connection from outside the hermeticallysealed unit to the coating on the inside of the unit may be required tocontrol the coating, and in such cases the connection through the metalsleeve must also be hermetic. To maintain hermeticity and also,electrical insulation between the feedthrough wire and the metal frame,a glass-to-metal seal may be used. The use of feedthroughs usingglass-to-metal seals is known in the electronic packaging industry. Thematerials chosen preferably have properties of wettability by glass,matched temperature coefficient of expansion, and low outgassing ratesat relevant temperatures, thereby making them suitable for use in vacuumsystems.

In a still further embodiment, a VGU would comprise an indicator forindicating whether the desired vacuum or reduced pressure atmosphere isstill contained within the inter-pane cavity of the VGU, i.e., that theVGU has not developed a leak. One such embodiment includes an indicatordisposed in the interior cavity of the VGU, the indicator changing colorif the vacuum level decreases and/or outside air enters the cavity. Theindicator may be incorporated on a label or other article disposed alongthe perimeter of the VGU so that it will be visible through the insidewindowpane.

In yet another embodiment, a gas-filled IGU would comprise an indicatorfor indicating the integrity of the IGU's seals, i.e., whether thedesired fill-gas had leaked out and/or whether gas has been exchangedbetween the interior and exterior of the IGU. Preferably, the indicatorwould comprise a color-changing article such as a label, visible throughthe inside windowpane. More preferably, a characteristic of the color,e.g., intensity or hue, would indicate the relative magnitude of theleak and/or loss of insulating properties.

While the invention has been shown or described in a further variety ofits forms, it should be apparent to those skilled in the art that it isnot limited to these embodiments, but is susceptible to still furtherchanges without departing from the scope of the invention.

In particular, it will be appreciated that the invention may bepracticed using various gases, including air, nitrogen, argon, krypton,xenon and mixtures of such gases, to fill the gap between thewindowpanes instead of a vacuum. The gases within the gap may be at areduced or partial pressure, in which case the spacer assembliesdescribed herein may still be necessary, or they may be at ambient orhigher pressure, in which case the spacer assemblies described hereinmay be omitted. In other embodiments, the spacer assemblies describedherein may be replaced by simplified spacer assemblies disposed onlyaround the periphery of the windowpanes.

1. A vacuum insulating glazing unit comprising: a first windowpane sheetformed of a transparent material and having a periphery surrounding aninterior region; a first sealing member having a first surface and asecond surface, the first surface being bonded to the periphery of thefirst windowpane sheet; a second windowpane sheet formed of atransparent material and having a periphery surrounding an interiorregion; a second sealing member having a first surface and a secondsurface, the first surface being bonded to the periphery of the secondwindowpane sheet, the second surfaces of the first and second sealingmembers being bonded to one another to create at least one sealed cavitybetween the interior regions of the first and second windowpane sheets;a spacer assembly including a third sheet formed of a transparentmaterial and having a plurality of stand-off members disposed onopposite sides thereof, the spacer assembly being disposed within thesealed cavity between the interior regions of the first and secondwindowpane sheets with the stand-off members facing the inner surfacesof the first and second windowpane sheets for maintaining a gaptherebetween; and wherein the atmosphere within the sealed cavity is avacuum.
 2. A vacuum insulating glazing unit in accordance with claim 1,wherein the third sheet is formed of two or more discrete layers.
 3. Avacuum insulating glazing unit in accordance with claim 2, wherein onediscrete layer is formed of a glass material and another discrete layeris formed of a different material.
 4. A vacuum insulating glazing unitin accordance with claim 2, wherein a coating is embedded between thediscrete layers, the coating being one of a low-emissivity coating, aU-V absorbing coating, a U-V reflecting coating, a color tint, anelectrochromatic coating, an electrochromeric coatings and ananti-reflective coating.
 5. An insulating glazing unit comprising: afirst windowpane sheet formed of a transparent material and having aperiphery surrounding an interior region; a second windowpane sheetformed of a transparent material and having a periphery surrounding aninterior region; at least one sealing assembly bonded between theperiphery of the first windowpane sheet and the periphery of the secondwindowpane sheet to create at least one sealed cavity between theinterior regions of the first and second windowpane sheets; a spacerassembly disposed within the sealed cavity between the interior regionsof the first and second windowpane sheets for maintaining a gaptherebetween, the spacer assembly being slidable with respect to atleast one of the first and second windowpane sheets; and the spacerassembly including a third sheet formed of a transparent material andhaving a plurality of stand-off members disposed on at least one sidethereof facing the inner surface of at least one of the first and secondwindowpane sheets.
 6. An insulating glazing unit in accordance withclaim 5, wherein the stand-off members are disposed on both sides of thethird sheet facing the inner surfaces of both the first and secondwindowpane sheets.
 7. An insulating glazing unit in accordance withclaim 5, wherein the stand-off members are disposed on only one side ofthe third sheet facing the inner surface of either the first or thesecond windowpane sheet.
 8. An insulating glazing unit in accordancewith claim 5, wherein the stand-off members are integrally formed aspart of the third sheet.
 9. An insulating glazing unit in accordancewith claim 5, wherein the stand-off members are formed separately fromthe third sheet and then affixed thereto before being placed within thesealed cavity.
 10. An insulating glazing unit in accordance with claim5, wherein the third sheet is formed of glass.
 11. An insulating glazingunit in accordance with claim 5, wherein the third sheet is formed of apolymer material.
 12. An insulating glazing unit in accordance withclaim 5, wherein the third sheet is formed of discrete layers ofdifferent materials laminated together.
 13. An insulating glazing unitin accordance with claim 5, wherein the third sheet is coated with atleast one of a low-emissivity coating, a U-V absorbing coating, a U-Vreflecting coating, a color tint, an electrochromatic coating, anelectrochromeric coatings and an anti-reflective coating.
 14. Aninsulating glazing unit in accordance with claim 5, wherein the sealingassembly further comprises: a first sealing member having a firstsurface and a second surface, the first surface being bonded to theperiphery of the first windowpane sheet; a second sealing member havinga first surface and a second surface, the first surface being bonded tothe periphery of the second windowpane sheet; and wherein the secondsurfaces of the first and second sealing members are bonded to oneanother.
 15. A vacuum insulating glazing unit comprising: a firstwindowpane sheet formed of a transparent material and having a peripherysurrounding an interior region; a second windowpane sheet formed of atransparent material and having a periphery surrounding an interiorregion; at least one sealing assembly bonded between the periphery ofthe first windowpane sheet and the periphery of the second windowpanesheet to create at least one sealed cavity between the interior regionsof the first and second windowpane sheets, the atmosphere within thesealed cavity being a vacuum; and a plurality of stand-off membersdisposed on the interior region of at least one of the first and secondwindowpane sheets for maintaining a gap therebetween within the sealedcavity, the stand-off members disposed on a particular windowpane sheetbeing slidable with respect to the other windowpane sheet.
 16. A vacuuminsulating glazing unit in accordance with claim 15, wherein thestand-off members are disposed on only one of the first and secondwindowpane sheets.
 17. A vacuum insulating glazing unit in accordancewith claim 15, wherein the stand-off members are disposed on both of thefirst and second windowpane sheets.
 18. A vacuum insulating glazing unitin accordance with claim 15, wherein the stand-off members areintegrally formed as part of the windowpane sheet upon which they aredisposed.
 19. A vacuum insulating glazing unit in accordance with claim15, wherein the stand-off members are formed separately from thewindowpane sheets and then affixed thereto before creation of the sealedcavity.
 20. A vacuum insulating glazing unit in accordance with claim15, wherein the sealing assembly further comprises: a first sealingmember having a first surface and a second surface, the first surfacebeing bonded to the periphery of the first windowpane sheet; a secondsealing member having a first surface and a second surface, the firstsurface being bonded to the periphery of the second windowpane sheet;and wherein the second surfaces of the first and second sealing membersare bonded to one another.